@article {16257,
	title = {The structure of a Bacteroides thetaiotaomicron carbohydrate-binding module provides new insight into the recognition of complex pectic polysaccharides by the human microbiome},
	year = {2023},
	note = {<p>n/a</p>
},
	month = {2023},
	pages = {100084},
	abstract = {<p>TheBacteroides thetaiotaomicronhas developed a consortium of enzymes capable of overcoming steric constraints and degrading, in a sequential manner, the complex rhamnogalacturonan II (RG-II) polysaccharide. BT0996 protein acts in the initial stages of the RGII depolymerisation, where its two catalytic modules remove the terminal monosaccharides from RG-II side chains A and B. BT0996 is modular and has three putative carbohydrate-binding modules (CBMs) for which the roles in the RG-II degradation are unknown. Here, we present the characterisation of themoduleat the C-terminal domain, which we designated BT0996C. The high-resolution structure obtained by X-ray crystallography reveals that the protein displays a typical β-sandwich fold with structural similarity to CBMs assigned to families 6 and 35. The distinctive features are: 1) the presence of several charged residues at the BT0996-C surface creating a large, broad positive lysine-rich patch that encompasses the putative binding site; and 2) the absence of the highly conserved binding-site signatures observed in CBMs from families 6 and 35, such as region A tryptophan and region C asparagine. These findings hint at a binding mode of BT0996-C not yet observed in its homologues. In line with this, carbohydrate microarrays and microscale thermophoresis show the ability of BT0996-C to bind α1-4-linked polygalacturonic acid, and that electrostatic interactions are essential for the recognition of the anionic polysaccharide. The results support the hypothesis that BT0996-C may have evolved to potentiate the action of BT0996 catalytic modules on the complex structure of RG-II by binding to the polygalacturonic acid backbone sequence.</p>
},
	keywords = {Carbohydrate Binding Module, Carbohydrates, Human Gut Microbiota, Rhamnogalacturonan II},
	isbn = {2590-1524},
	url = {https://www.sciencedirect.com/science/article/pii/S2590152422000253},
	author = {Trov{\~a}o, Filipa and Correia, Viviana G. and Louren{\c c}o, Frederico M. and Ribeiro, Diana O. and Carvalho, Ana Lu{\'\i}sa and Palma, Angelina S. and Pinheiro, Benedita A.}
}
