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Single-binding mode integration of hemicellulose degrading enzymes via adaptor scaffoldins in Ruminococcus flavefaciens cellulosome

DOI: 10.1074/jbc.M116.761643 DOI Help

Authors: Pedro Bule (Universidade de Lisboa) , Victor Diogo Alves (Universidade de Lisboa) , André Leitão (Universidade de Lisboa) , Luis M. A. Ferreira (Universidade de Lisboa) , Edward A. Bayer (The Weizmann Institute of Science) , Steven P. Smith (Queen's University) , Harry J Gilbert (University of Newcastle) , Shabir Najmudin (Universidade de Lisboa) , Carlos M. G. A. Fontes (Universidade de Lisboa)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry

State: Published (Approved)
Published: November 2016
Diamond Proposal Number(s): 8425

Abstract: The assembly of one of Nature most elaborate multi-enzyme complexes, the cellulosome, results from the binding of enzyme-borne dockerins to reiterated cohesin domains located in a non-catalytic primary scaffoldin. Generally, dockerins present two similar cohesin binding interfaces that support a dual binding mode. The dynamic integration of enzymes in cellulosomes, afforded by the dual binding mode, is believed to incorporate additional flexibility in highly populated multi-enzyme complexes. Ruminococcus flavefaciens, the primary degrader of plant structural carbohydrates in the rumen of mammals, uses a portfolio of more than 220 different enzymes to assemble the most intricate cellulosome known to date. A sequence-based analysis organized R. flavefaciens dockerins into six groups. Strikingly, a subset of R. flavefaciens cellulosomal enzymes, comprising dockerins of groups 3 and 6, were shown to be indirectly incorporated into primary scaffoldins, via an adaptor scaffoldin termed ScaC. Here we report the crystal structure of a group 3 R. flavefaciens dockerin, Doc3, in complex with ScaC cohesin. Doc3 is unusual as it presents a large cohesin-interacting surface that lacks the structural symmetry required to support a dual binding mode. In addition, dockerins of groups 3 and 6, which bind exclusively to ScaC cohesin, display a conserved mechanism of protein recognition that is similar to Doc3. Group 3 and 6 dockerins are predominantly appended to hemicellulose degrading enzymes. Thus, single binding mode dockerins interacting with adaptor scaffoldins exemplify an evolutionary pathway developed by R. flavefaciens to recruit hemicellulases to the sophisticated cellulosomes acting on the gastro intestinal tract of mammals.

Journal Keywords: cellulase; cellulose; cellulosome; protein structure; protein-protein interaction; cohesin; dockerin

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I04-Macromolecular Crystallography

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