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Duarte, Marlene, Aldino Viegas, Victor D. Alves, José A. M. Prates, Luís M. A. Ferreira, Shabir Najmudin, Eurico J. Cabrita, Ana Luísa Carvalho, Carlos M. G. A. Fontes, and Pedro Bule. "A dual cohesin–dockerin complex binding mode in Bacteroides cellulosolvens contributes to the size and complexity of its cellulosome." (2021): 100552. AbstractWebsite

The Cellulosome is an intricate macromolecular protein complex that centralizes the cellulolytic efforts of many anaerobic microorganisms through the promotion of enzyme synergy and protein stability. The assembly of numerous carbohydrate processing enzymes into a macromolecular multi-protein structure results from the interaction of enzyme-borne dockerin modules with repeated cohesin modules present in non-catalytic scaffold proteins, termed scaffoldins. Cohesin–dockerin (Coh–Doc) modules are typically classified into different types, depending on structural conformation and cellulosome role. Thus, type I Coh–Doc complexes are usually responsible for enzyme integration into the cellulosome, while type II Coh–Doc complexes tether the cellulosome to the bacterial wall. In contrast to other known cellulosomes, cohesin types from Bacteroides cellulosolvens, a cellulosome-producing bacterium capable of utilizing cellulose and cellobiose as carbon sources, are reversed for all scaffoldins, i.e., the type II cohesins are located on the enzyme-integrating primary scaffoldin, whereas the type I cohesins are located on the anchoring scaffoldins. It has been previously shown that type I B. cellulosolvens interactions possess a dual-binding mode that adds flexibility to scaffoldin assembly. Herein, we report the structural mechanism of enzyme recruitment into B. cellulosolvens cellulosome and the identification of the molecular determinants of its type II cohesin–dockerin interactions. The results indicate that, unlike other type II complexes, these possess a dual binding mode of interaction, akin to type I complexes. Therefore, the plasticity of dual-binding mode interactions seems to play a pivotal role in the assembly of B. cellulosolvens cellulosome, which is consistent with its unmatched complexity and size.

Goodfellow, Brian J., Filipe Freire, Ana Luísa Carvalho, Susana S. Aveiro, Peggy Charbonnier, Jean-Marc Moulis, Leonildo Delgado, Gloria C. Ferreira, João E. Rodrigues, Pierre Poussin-Courmontagne, Catherine Birck, Alastair McEwen, and Anjos L. Macedo. "The SOUL family of heme-binding proteins: Structure and function 15 years later." 448 (2021): 214189. AbstractWebsite

The SOUL, or heme-binding protein HBP/SOUL, family represents a group of evolutionary conserved putative heme-binding proteins that contains a number of members in animal, plant andbacterial species. The structures of the murine form of HEBP1, or p22HBP, and the human form of HEBP2, or SOUL, have been determined in 2006 and 2011 respectively. In this work we discuss the structures of HEBP1 and HEBP2 in light of new X-ray data for heme bound murine HEBP1. The interaction between tetrapyrroles and HEBP1, initially proven to be hydrophobic in nature, was thought to also involve electrostatic interactions between heme propionate groups and positively charged amino acid side chains. However, the new X-ray structure, and results from murine HEBP1 variants and human HEBP1, confirm the hydrophobic nature of the heme-HEBP1 interaction, resulting in Kd values in the low nanomolar range, and rules out any electrostatic stabilization. Results from NMR relaxation time measurements for human HEBP1 describe a rigid globular protein with no change in motional regime upon heme binding. X-ray structures deposited in the PDB for human HEBP2 are very similar to each other and to the new heme-bound murine HEBP1 X-ray structure (backbone rmsd ca. 1 Å). Results from a HSQC spectrum centred on the histidine side chain Nδ-proton region for HEBP2 confirm that HEBP2 does not bind heme via H42 as no chemical shift differences were observed upon heme addition for backbone NH and Nδ protons. A survey of the functions attributed to HEBP1 and HEBP2 over the last 20 years span a wide range of cellular pathways. Interestingly, many of them are specific to higher eukaryotes, particularly mammals and a potential link between heme release under oxidative stress and human HEBP1 is also examined using recent data. However, at the present moment, trying to relate function to the involvement of heme or tetrapyrrole binding, specifically, makes little sense with our current biological knowledge and can only be applied to HEBP1, as HEBP2 does not interact with heme. We suggest that it may not be justified to call this very small family of proteins, heme-binding proteins. The family may be more correctly called “the SOUL family of proteins related to cellular fate” as, even though only HEBP1 binds heme tightly, both proteins may be involved in cell survival and/or proliferation.

Lima, Carlos D. L., Helena Coelho, Ana Gimeno, Filipa Trovão, Ana Diniz, Jorge S. Dias, Jesús Jiménez-Barbero, Francisco Corzana, Ana Luísa Carvalho, Eurico J. Cabrita, and Filipa Marcelo. "Structural insights into the molecular recognition mechanism of the cancer and pathogenic epitope, LacdiNAc by immune-related lectins." Chemistry – A European JournalChemistry – A European Journal. n/a.n/a (2021). AbstractWebsite

Interactions of glycan-specific epitopes to human lectin receptors represent novel immune checkpoints for investigating cancer and infection diseases. By employing a multidisciplinary approach that combines isothermal titration calorimetry, NMR spectroscopy, molecular dynamics simulations, and X-ray crystallography, we disclosed the molecular determinants that govern the recognition of the tumour and pathogenic glycobiomarker LacdiNAc (GalNAc?1-4GlcNAc, LDN), including their comparison with the ubiquitous LacNAc epitope (Gal?1-4GlcNAc, LN), by two human immune-related lectins, galectin-3 (hGal-3) and the macrophage galactose C-type lectin (hMGL). A different mechanism of binding and interactions is observed for the hGal-3/LDN and hMGL/LDN complexes, which explains the remarkable difference in the binding specificity of LDN and LN by these two lectins. The new structural clues reported herein are fundamental for the chemical design of mimetics targeting hGal-3/hMGL recognition process.

dos Santos, Raquel, Maria João Romão, Ana Cecília A. Roque, and Ana Luísa Carvalho. "Magnetic particles used in a new approach for designed protein crystallization." CrystEngComm. 23 (2021): 1083-1090. AbstractWebsite

After more than one hundred and thirty thousand protein structures determined by X-ray crystallography{,} the challenge of protein crystallization for 3D structure determination remains. In the quest for additives for efficient protein crystallization{,} inorganic materials emerge as an alternative. Magnetic particles (MPs) are versatile inorganic materials{,} easy to use{,} modify and manipulate in a wide range of biological assays. The potential of using functionalised MPs as crystallization chaperones for protein crystallization was shown in this work. MPs with distinct coatings were rationally designed to promote protein crystallization by affinity-triggered heterogeneous nucleation. Hen egg white lysozyme (HEWL) and trypsin{,} were crystallized in the presence of MPs either bare or coated with a polysaccharide (chitin) or a protein (casein){,} respectively. The addition of MPs was characterized in terms of bound protein to the MPs{,} crystal morphology{,} time-lapse of crystal emergence{,} crystallization yield fold change and crystal diffraction quality for structure determination. The MPs additives have shown to bind to the respective target protein{,} and to promote nucleation and crystal growth without compromising crystal morphology. On the other hand{,} MPs addition led to faster detectable crystal emergence and up to 13 times higher crystallization yield{,} addressing some the challenges in protein crystallization{,} the main bottleneck of macromolecular crystallography. Structure determination of the protein crystallized in the presence of MPs revealed that the structural characteristics of the protein remained unchanged{,} as shown by the superposition with PDB annotated proteins. Moreover{,} and unlike most reported cases{,} it was possible to exclude the inhibitor benzamidine during trypsin crystallisation{,} which is a remarkable result opening new prospects in enzyme engineering and drug design. Our results show that MPs coated with affinity ligands to target proteins can be used as controlled and tailor-made crystallization inducers.

Polino, M., H. S. Rho, M. P. Pina, R. Mallada, AL Carvalho, MJ Romão, Isabel Coelhoso, J. G. E. Gardeniers, J. G. Crespo, and Carla A. M. Portugal. "Protein Crystallization in a Microfluidic Contactor with Nafion®117 Membranes." Membranes. 11 (2021). AbstractWebsite

Protein crystallization still remains mostly an empirical science, as the production of crystals with the required quality for X-ray analysis is dependent on the intensive screening of the best protein crystallization and crystal’s derivatization conditions. Herein, this demanding step was addressed by the development of a high-throughput and low-budget microfluidic platform consisting of an ion exchange membrane (117 Nafion® membrane) sandwiched between a channel layer (stripping phase compartment) and a wells layer (feed phase compartment) forming 75 independent micro-contactors. This microfluidic device allows for a simultaneous and independent screening of multiple protein crystallization and crystal derivatization conditions, using Hen Egg White Lysozyme (HEWL) as the model protein and Hg2+ as the derivatizing agent. This microdevice offers well-regulated crystallization and subsequent crystal derivatization processes based on the controlled transport of water and ions provided by the 117 Nafion® membrane. Diffusion coefficients of water and the derivatizing agent (Hg2+) were evaluated, showing the positive influence of the protein drop volume on the number of crystals and crystal size. This microfluidic system allowed for crystals with good structural stability and high X-ray diffraction quality and, thus, it is regarded as an efficient tool that may contribute to the enhancement of the proteins’ crystals structural resolution.

dos Santos, Raquel, Inês Iria, Ana M. Manuel, Ana P. Leandro, Catarina A. C. Madeira, Joao Goncalves, Ana Luísa Carvalho, and Ana Cecília Roque. "Magnetic Precipitation: A New Platform for Protein Purification." Biotechnology JournalBiotechnology Journal. n/a.n/a (2020): 2000151. AbstractWebsite

One of the trends in downstream processing comprises the use of ?anything-but-chromatography? methods to overcome the current downfalls of standard packed-bed chromatography. Precipitation and magnetic separation are two techniques already proven to accomplish protein purification from complex media, yet never used in synergy. With the aim to capture antibodies directly from crude extracts, a new approach combining precipitation and magnetic separation was developed and named as affinity magnetic precipitation. A precipitation screening, based on the Hofmeister series, and a commercial precipitation kit were tested with affinity magnetic particles to assess the best condition for antibody capture from human serum plasma and clarified cell supernatant. The best conditions were obtained when using PEG3350 as precipitant at 4°C for 1h, reaching 80% purity and 50% recovery of polyclonal antibodies from plasma, and 99% purity with 97% recovery yield of anti-TNFα mAb from cell supernatants. These results show that the synergetic use of precipitation and magnetic separation can represent an alternative for the efficient capture of antibodies. This article is protected by copyright. All rights reserved

Gomes, Ana Sara, Helena Ramos, Sara Gomes, Joana B. Loureiro, Joana Soares, Valentina Barcherini, Paola Monti, Gilberto Fronza, Carla Oliveira, Lucília Domingues, Margarida Bastos, Daniel F. A. R. Dourado, Ana Luísa Carvalho, Maria João Romão, Benedita Pinheiro, Filipa Marcelo, Alexandra Carvalho, Maria M. M. Santos, and Lucília Saraiva. "SLMP53-1 interacts with wild-type and mutant p53 DNA-binding domain and reactivates multiple hotspot mutations." 1864.1 (2020): 129440. AbstractWebsite

BackgroundHalf of human cancers harbour TP53 mutations that render p53 inactive as a tumor suppressor. As such, reactivation of mutant (mut)p53 through restoration of wild-type (wt)-like function represents one of the most promising therapeutic strategies in cancer treatment. Recently, we have reported the (S)-tryptophanol-derived oxazoloisoindolinone SLMP53-1 as a new reactivator of wt and mutp53 R280K with in vitro and in vivo p53-dependent antitumor activity. The present work aimed a mechanistic elucidation of mutp53 reactivation by SLMP53-1.
Methods and results
By cellular thermal shift assay (CETSA), it is shown that SLMP53-1 induces wt and mutp53 R280K thermal stabilization, which is indicative of intermolecular interactions with these proteins. Accordingly, in silico studies of wt and mutp53 R280K DNA-binding domain with SLMP53-1 unveiled that the compound binds at the interface of the p53 homodimer with the DNA minor groove. Additionally, using yeast and p53-null tumor cells ectopically expressing distinct highly prevalent mutp53, the ability of SLMP53-1 to reactivate multiple mutp53 is evidenced.
SLMP53-1 is a p53-activating agent with the ability to directly target wt and a set of hotspot mutp53.
General Significance
This work reinforces the encouraging application of SLMP53-1 in the personalized treatment of cancer patients harboring distinct p53 status.

Ribeiro, Diana O., Aldino Viegas, Virgínia M. R. Pires, João Medeiros-Silva, Pedro Bule, Wengang Chai, Filipa Marcelo, Carlos M. G. A. Fontes, Eurico J. Cabrita, Angelina S. Palma, and Ana Luísa Carvalho. "Molecular basis for the preferential recognition of β1,3-1,4-glucans by the family 11 carbohydrate-binding module from Clostridium thermocellum." The FEBS Journal. 287 (2020): 2723-2743. AbstractWebsite

Understanding the specific molecular interactions between proteins and β1,3-1,4-mixed-linked d-glucans is fundamental to harvest the full biological and biotechnological potential of these carbohydrates and of proteins that specifically recognize them. The family 11 carbohydrate-binding module from Clostridium thermocellum (CtCBM11) is known for its binding preference for β1,3-1,4-mixed-linked over β1,4-linked glucans. Despite the growing industrial interest of this protein for the biotransformation of lignocellulosic biomass, the molecular determinants of its ligand specificity are not well defined. In this report, a combined approach of methodologies was used to unravel, at a molecular level, the ligand recognition of CtCBM11. The analysis of the interaction by carbohydrate microarrays and NMR and the crystal structures of CtCBM11 bound to β1,3-1,4-linked glucose oligosaccharides showed that both the chain length and the position of the β1,3-linkage are important for recognition, and identified the tetrasaccharide Glcβ1,4Glcβ1,4Glcβ1,3Glc sequence as a minimum epitope required for binding. The structural data, along with site-directed mutagenesis and ITC studies, demonstrated the specificity of CtCBM11 for the twisted conformation of β1,3-1,4-mixed-linked glucans. This is mediated by a conformation–selection mechanism of the ligand in the binding cleft through CH-π stacking and a hydrogen bonding network, which is dependent not only on ligand chain length, but also on the presence of a β1,3-linkage at the reducing end and at specific positions along the β1,4-linked glucan chain. The understanding of the detailed mechanism by which CtCBM11 can distinguish between linear and mixed-linked β-glucans strengthens its exploitation for the design of new biomolecules with improved capabilities and applications in health and agriculture. Database Structural data are available in the Protein Data Bank under the accession codes 6R3M and 6R31.

Outis, Mani, Vitor Rosa, César AT Laia, João Carlos Lima, Sónia Barroso, Ana Luísa Carvalho, Maria José Calhorda, and Teresa Avilés. "Synthesis, Crystal Structure, and DFT Study of Two New Dinuclear Copper(I) Complexes Bearing Ar-BIAN Ligands Functionalized with NO2 Groups." European Journal of Inorganic Chemistry. 2020 (2020): 2900-2911. AbstractWebsite

{Two new bis(aryl-imino)-acenaphthene, Ar-BIAN (Ar = 2

Peixoto, Daniela, Gabriela Malta, Hugo Cruz, Sónia Barroso, Ana Luísa Carvalho, Luísa M. Ferreira, and Paula S. Branco. "N-Heterocyclic Olefin Catalysis for the Ring Opening of Cyclic Amidine Compounds: A Pathway to the Synthesis of ε-Caprolactam- and γ-Lactam-Derived Amines." The Journal of Organic ChemistryThe Journal of Organic Chemistry (2019). AbstractWebsite
Correia, Viviana G., Benedita A. Pinheiro, Ana Luísa Carvalho, and Angelina S. Palma. "Resistance to Aminoglycosides." Antibiotic Drug Resistance. John Wiley & Sons, Ltd, 2019. 1-38. Abstract

Summary The emergence of bacterial resistance to different antibiotics in clinical use, together with the knowledge on the mechanisms by which bacteria resist the action of aminoglycosides, have contributed to the renewed interest in these molecules as potential antimicrobials. Here, we give an overview on natural and semisynthetic aminoglycosides and their structural features and modes of action, focusing on the structural insight underlying resistance mechanisms. Developments on carbohydrate chemistry and microarray technology are highlighted as powerful approaches toward generation of new aminoglycosides and for screening their interactions with RNAs and proteins. The link between antibiotic uptake and the human gut microbiome is also addressed, focusing on gut microbiome function and composition, antibiotic-induced alterations in host health, and antibiotic resistance. In addition, strategies to modulate human microbiome responses to antibiotics are discussed as novel approaches for aminoglycoside usage and for the effectiveness of antibiotic therapy.

Carvalho, Ana Luísa, Teresa Santos-Silva, Maria João Romão, J. Eurico, and Filipa Marcelo. "{CHAPTER 2 Structural Elucidation of Macromolecules}." Essential Techniques for Medical and Life Scientists: A Guide to Contemporary Methods and Current Applications with the Protocols. BENTHAM SCIENCE PUBLISHERS, 2018. 30-91. Abstract


Bule, Pedro, Virgínia M. R. Pires, Victor D. Alves, Ana Luísa Carvalho, José A. M. Prates, Luís M. A. Ferreira, Steven P. Smith, Harry J. Gilbert, Ilit Noach, Edward A. Bayer, Shabir Najmudin, and Carlos M. G. A. Fontes. "Higher order scaffoldin assembly in Ruminococcus flavefaciens cellulosome is coordinated by a discrete cohesin-dockerin interaction." Scientific Reports. 8.1 (2018): 6987. AbstractWebsite

Cellulosomes are highly sophisticated molecular nanomachines that participate in the deconstruction of complex polysaccharides, notably cellulose and hemicellulose. Cellulosomal assembly is orchestrated by the interaction of enzyme-borne dockerin (Doc) modules to tandem cohesin (Coh) modules of a non-catalytic primary scaffoldin. In some cases, as exemplified by the cellulosome of the major cellulolytic ruminal bacterium Ruminococcus flavefaciens, primary scaffoldins bind to adaptor scaffoldins that further interact with the cell surface via anchoring scaffoldins, thereby increasing cellulosome complexity. Here we elucidate the structure of the unique Doc of R. flavefaciens FD-1 primary scaffoldin ScaA, bound to Coh 5 of the adaptor scaffoldin ScaB. The RfCohScaB5-DocScaA complex has an elliptical architecture similar to previously described complexes from a variety of ecological niches. ScaA Doc presents a single-binding mode, analogous to that described for the other two Coh-Doc specificities required for cellulosome assembly in R. flavefaciens. The exclusive reliance on a single-mode of Coh recognition contrasts with the majority of cellulosomes from other bacterial species described to date, where Docs contain two similar Coh-binding interfaces promoting a dual-binding mode. The discrete Coh-Doc interactions observed in ruminal cellulosomes suggest an adaptation to the exquisite properties of the rumen environment.

Santarsia, Sabrina, Ana Sofia Grosso, Filipa Trovão, Jesús Jiménez-Barbero, Ana Luísa Carvalho, Cristina Nativi, and Filipa Marcelo. "Molecular recognition of a Thomsen-Friedenreich antigen mimetic targeting human galectin-3." ChemMedChem. Aug 9. doi: 10.1002/cmdc.201800525. [Epub ahead of print] (2018). AbstractWebsite

Overexpression of the Thomsen-Friedenreich (TF) antigen in cell membrane proteins occurs in 90% of adenocarcinomas. Additionally, the binding of the TF-antigen to human galectin-3 (Gal-3), also frequently overexpressed in malignancy, promotes cancer progression and metastasis. In this context, structures that interfere with this specific interaction display the potential to prevent cancer metastasis. Herein, a multidisciplinary approach, combining the optimized synthesis of a TF-antigen mimetic with NMR, X-ray crystallography methods and isothermal titration calorimetry assays has been employed to unravel the molecular structural details that govern the Gal-3/TF-mimetic interaction. The TF-mimetic presents a binding affinity for Gal-3 similar to the TF-natural antigen and retains the binding epitope and the bioactive conformation observed for the native antigen. Furthermore, from a thermodynamic perspective a decrease in the enthalpic contribution was observed for the Gal-3/TF-mimetic complex, however this behaviour is compensated by a favourable entropy gain. From a structural perspective, these results establish our TF-mimetic as a scaffold to design multivalent solutions to potentially interfere with Gal-3 aberrant interactions and likely be used to hamper Gal-3-mediated cancer cells adhesion and metastasis.

Branco, Paula S., Daniela Peixoto, Margarida Figueiredo, Gabriela Malta, Catarina Roma-Rodrigues, Pedro Viana Batista, Alexandra R. Fernandes, Sónia Barroso, Ana Luisa Carvalho, Carlos A. M. Afonso, and Luísa Maria Ferreira. "Synthesis, cytotoxicity evaluation in human cell lines and in vitro DNA interaction of a hetero arylidene-9(10H)-anthrone." European Journal of Organic Chemistry (2018): n/a–n/a. AbstractWebsite

A new and never yet reported hetero arylidene-9(10H)-anthrone structure (4) was unexpectedly isolated on reaction of 1,2-dimethyl-3-ethylimidazolium iodide (2) and 9-anthracenecarboxaldehyde (3) under basic conditions. Its structure was unequivocally attributed by X-ray crystallography. No cytotoxicity in human healthy fibroblasts and in two different cancer cell lines was observed indicating its applicability in biological systems. Compound 4 interacts with CT-DNA by intercalation between the adjacent base pairs of DNA with a high binding affinity (Kb = 2.0(± 0.20) x 105 M-1) which is 10x higher than that described for doxorubicin (Kb = 3.2 (±0.23) × 104 M-1). Furthermore, compound 4 quenches the fluorescence emission of GelRed-CT-DNA system with a quenching constant (KSV) of 3.3(±0.3) x 103 M-1 calculated by the Stern-Volmer equation.

Gomes, Ana Sara, Filipa Trovão, Benedita Andrade Pinheiro, Filipe Freire, Sara Gomes, Carla Oliveira, Lucília Domingues, Maria João Romão, Lucília Saraiva, and Ana Luísa Carvalho. "The Crystal Structure of the R280K Mutant of Human p53 Explains the Loss of DNA Binding." International Journal of Molecular Sciences. 19 (2018). AbstractWebsite

The p53 tumor suppressor is widely found to be mutated in human cancer. This protein is regarded as a molecular hub regulating different cell responses, namely cell death. Compelling data have demonstrated that the impairment of p53 activity correlates with tumor development and maintenance. For these reasons, the reactivation of p53 function is regarded as a promising strategy to halt cancer. In the present work, the recombinant mutant p53R280K DNA binding domain (DBD) was produced for the first time, and its crystal structure was determined in the absence of DNA to a resolution of 2.0 Å. The solved structure contains four molecules in the asymmetric unit, four zinc(II) ions, and 336 water molecules. The structure was compared with the wild-type p53 DBD structure, isolated and in complex with DNA. These comparisons contributed to a deeper understanding of the mutant p53R280K structure, as well as the loss of DNA binding related to halted transcriptional activity. The structural information derived may also contribute to the rational design of mutant p53 reactivating molecules with potential application in cancer treatment.

Kumar, Krishan, Márcia Correia, Virgínia R. Pires, Arun Dhillon, Kedar Sharma, Vikky Rajulapati, Carlos M. G. A. Fontes, Ana Luísa Carvalho, and Arun Goyal. "Novel insights into the degradation of β-1,3-glucans by the cellulosome of Clostridium thermocellum revealed by structure and function studies of a family 81 glycoside hydrolase." International Journal of Biological Macromolecules (2018): -. AbstractWebsite

Abstract The family 81 glycoside hydrolase (GH81) from Clostridium thermocellum is a β-1,3-glucanase belonging to cellulosomal complex. The gene encoding \{GH81\} from Clostridium thermocellum (CtLam81A) was cloned and expressed displaying a molecular mass of  82 kDa. CtLam81A showed maximum activity against laminarin (100 U/mg), followed by curdlan (65 U/mg), at pH 7.0 and 75 °C. CtLam81A displayed Km, 2.1 ± 0.12 mg/ml and Vmax, 109 ± 1.8 U/mg, against laminarin under optimized conditions. CtLam81A activity was significantly enhanced by Ca2+ or Mg2+ ions. Melting curve analysis of CtLam81A showed an increase in melting temperature from 91 °C to 96 °C by Ca2+ or Mg2+ ions and decreased to 82 °C by EDTA, indicating that Ca2+ and Mg2+ ions may be involved in catalysis and in maintaining structural integrity. \{TLC\} and MALDI-TOF analysis of β-1,3-glucan hydrolysed products released initially, showed β-1,3-glucan-oligosaccharides degree of polymerization (DP) from \{DP2\} to DP7, confirming an endo-mode of action. The catalytically inactive mutant CtLam81A-E515A generated by site-directed mutagenesis was co-crystallized and tetragonal crystals diffracting up to 1.4 Å resolution were obtained. CtLam81A-E515A contained 15 α-helices and 38 β-strands forming a four-domain structure viz. a β-sandwich domain I at N-terminal, an α/β-domain II, an (α/α)6 barrel domain III, and a small 5-stranded β-sandwich domain IV.

Ribeiro, Diana O., Benedita A. Pinheiro, Ana Luisa Carvalho, and Angelina S. Palma. "Targeting protein-carbohydrate interactions in plant cell-wall biodegradation: the power of carbohydrate microarrays." Carbohydrate Chemistry: Chemical and Biological Approaches Volume 43. Vol. 43. The Royal Society of Chemistry, 2018. 159-176. Abstract

The plant cell-wall is constituted by structurally diverse polysaccharides. The biodegradation of these is a crucial process for life sustainability. Cellulolytic microorganisms are highly efficient in this process by assembling modular architectures of carbohydrate-active enzymes with appended non-catalytic carbohydrate-binding modules (CBMs). Carbohydrate microarrays offer high-throughput and sensitive tools for uncovering carbohydrate-binding specificities of CBMs{,} which is pivotal to understand the function of these modules in polysaccharide biodegradation mechanisms. Features of this technology will be here briefly reviewed with highlights of microarray approaches to study plant-carbohydrates and CBM-carbohydrate interactions{,} along with an overview of plant polysaccharides and microorganisms strategies for their recognition.

Kryshtafovych, Andriy, Reinhard Albrecht, Arnaud Baslé, Pedro Bule, Alessandro T. Caputo, Ana Luisa Carvalho, Kinlin L. Chao, Ron Diskin, Krzysztof Fidelis, Carlos M. G. A. Fontes, Folmer Fredslund, Harry J. Gilbert, Celia W. Goulding, Marcus D. Hartmann, Christopher S. Hayes, Osnat Herzberg, Johan C. Hill, Andrzej Joachimiak, Gert-Wieland Kohring, Roman I. Koning, Leila {Lo Leggio}, Marco Mangiagalli, Karolina Michalska, John Moult, Shabir Najmudin, Marco Nardini, Valentina Nardone, Didier Ndeh, Thanh H. Nguyen, Guido Pintacuda, Sandra Postel, Mark J. van Raaij, Pietro Roversi, Amir Shimon, Abhimanyu K. Singh, Eric J. Sundberg, Kaspars Tars, Nicole Zitzmann, and Torsten Schwede. "Target highlights from the first post-PSI CASP experiment (CASP12, May-August 2016)." Proteins: Structure, Function, and Bioinformatics (2017). AbstractWebsite

The functional and biological significance of the selected CASP12 targets are described by the authors of the structures. The crystallographers discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP12 experiment. This article is protected by copyright. All rights reserved.

Hussain, Abid, Ana T. S. Semeano, Susana I. C. J. Palma, Ana S. Pina, José Almeida, Bárbara F. Medrado, Ana C. C. S. Pádua, Ana L. Carvalho, Madalena Dionísio, Rosamaria W. C. Li, Hugo Gamboa, Rein V. Ulijn, Jonas Gruber, and Ana C. A. Roque. "Tunable gas sensing gels by cooperative assembly." Advanced Functional Materials. just accep (2017): xx. AbstractWebsite


Pires, Virgínia M. R., Pedro M. M. Pereira, Joana L. A. Brás, Márcia Correia, Vânia Cardoso, Pedro Bule, Victor D. Alves, Shabir Najmudin, Immacolata Venditto, Luís M. A. Ferreira, Maria João Romão, Ana Luísa Carvalho, Carlos M. G. A. Fontes, and Duarte Miguel Prazeres. "Stability and ligand promiscuity of type A carbohydrate-binding modules are illustrated by the structure of Spirochaeta thermophila StCBM64C." Journal of Biological Chemistry. 292 (2017): 4847-4860. AbstractWebsite

Deconstruction of cellulose, the most abundant plant cell wall polysaccharide, requires the cooperative activity of a large repertoire of microbial enzymes. Modular cellulases contain non-catalytic type A Carbohydrate-Binding Modules (CBMs) that specifically bind to the crystalline regions of cellulose, thus promoting enzyme efficacy through proximity and targeting effects. Although type A CBMs play a critical role in cellulose recycling, their mechanism of action remains poorly understood. Here we produced a library of recombinant CBMs representative of the known diversity of type A modules. The binding properties of 40 CBMs, in fusion with an N-terminal green fluorescence protein (GFP) domain, revealed that type A CBMs possess the ability to recognize different crystalline forms of cellulose and chitin over a wide range of temperatures, pHs and ionic strengths. A Spirochaeta thermophila CBM64, in particular, displayed plasticity in its capacity to bind both crystalline and soluble carbohydrates under a wide range of extreme conditions. The structure of S. thermophila StCBM64C revealed an untwisted, flat, carbohydrate-binding interface comprising the side chains of four tryptophan residues in a coplanar linear arrangement. Significantly, two highly conserved asparagine side chains, each one located between two tryptophan residues, are critical to insoluble and soluble glucan recognition but not to bind xyloglucan. Thus, CBM64 compact structure and its extended and versatile ligand interacting platform illustrates how type A CBMs target their appended plant cell wall degrading enzymes to a diversity of recalcitrant carbohydrates under a wide range of environmental conditions.

Kowacz, Magdalena, Mateusz Marchel, Lina Juknaité, José M. S. S. Esperança, Maria João Romão, Ana Luísa Carvalho, and Luís Paulo N. Rebelo. "Infrared light-induced protein crystallization. Structuring of protein interfacial water and periodic self-assembly." Journal of Crystal Growth. 457 (2017): 362-368. AbstractWebsite

We show that a physical trigger, a non-ionizing infrared (IR) radiation at wavelengths strongly absorbed by liquid water, can be used to induce and kinetically control protein (periodic) self-assembly in solution. This phenomenon is explained by considering the effect of IR light on the structuring of protein interfacial water. Our results indicate that the IR radiation can promote enhanced mutual correlations of water molecules in the protein hydration shell. We report on the radiation-induced increase in both the strength and cooperativeness of H-bonds. The presence of a structured dipolar hydration layer can lead to attractive interactions between like-charged biomacromolecules in solution (and crystal nucleation events). Furthermore, our study suggests that enveloping the protein within a layer of structured solvent (an effect enhanced by IR light) can prevent the protein non-specific aggregation favoring periodic self-assembly. Recognizing the ability to affect protein-water interactions by means of IR radiation may have important implications for biological and bio-inspired systems.

Bule, Pedro, Victor D. Alves, Vered Israeli-Ruimy, Ana L. Carvalho, Luís M. A. Ferreira, Steven P. Smith, Harry J. Gilbert, Shabir Najmudin, Edward A. Bayer, and Carlos M. G. A. Fontes. "Assembly of Ruminococcus flavefaciens cellulosome revealed by structures of two cohesin-dockerin complexes." Scientific Reports. 7.1 (2017): 759. AbstractWebsite

Cellulosomes are sophisticated multi-enzymatic nanomachines produced by anaerobes to effectively deconstruct plant structural carbohydrates. Cellulosome assembly involves the binding of enzyme-borne dockerins (Doc) to repeated cohesin (Coh) modules located in a non-catalytic scaffoldin. Docs appended to cellulosomal enzymes generally present two similar Coh-binding interfaces supporting a dual-binding mode, which may confer increased positional adjustment of the different complex components. Ruminococcus flavefaciens’ cellulosome is assembled from a repertoire of 223 Doc-containing proteins classified into 6 groups. Recent studies revealed that Docs of groups 3 and 6 are recruited to the cellulosome via a single-binding mode mechanism with an adaptor scaffoldin. To investigate the extent to which the single-binding mode contributes to the assembly of R. flavefaciens cellulosome, the structures of two group 1 Docs bound to Cohs of primary (ScaA) and adaptor (ScaB) scaffoldins were solved. The data revealed that group 1 Docs display a conserved mechanism of Coh recognition involving a single-binding mode. Therefore, in contrast to all cellulosomes described to date, the assembly of R. flavefaciens cellulosome involves single but not dual-binding mode Docs. Thus, this work reveals a novel mechanism of cellulosome assembly and challenges the ubiquitous implication of the dual-binding mode in the acquisition of cellulosome flexibility.

Polino, Mariella, Ana Luı́sa Carvalho, Lina Juknaitė, Carla A. M. Portugal, Isabel M. Coelhoso, Maria João Romão, and João G. Crespo. "Ion-Exchange Membranes for Stable Derivatization of Protein Crystals." Crystal Growth & DesignCrystal Growth & Design (2017). AbstractWebsite
dos Santos, Raquel, Ana Luísa Carvalho, and Cecília A. A. Roque. "Renaissance of protein crystallization and precipitation in biopharmaceuticals purification." Biotechnology Advances (2017): -. AbstractWebsite

Abstract The current chromatographic approaches used in protein purification are not keeping pace with the increasing biopharmaceutical market demand. With the upstream improvements, the bottleneck shifted towards the downstream process. New approaches rely in Anything But Chromatography methodologies and revisiting former techniques with a bioprocess perspective. Protein crystallization and precipitation methods are already implemented in the downstream process of diverse therapeutic biological macromolecules, overcoming the current chromatographic bottlenecks. Promising work is being developed in order to implement crystallization and precipitation in the purification pipeline of high value therapeutic molecules. This review focuses in the role of these two methodologies in current industrial purification processes, and highlights their potential implementation in the purification pipeline of high value therapeutic molecules, overcoming chromatographic holdups.