Assembly of Ruminococcus flavefaciens cellulosome revealed by structures of two cohesin-dockerin complexes

Citation:
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.

Abstract:

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.

Notes:

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