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Cell-surface Attachment of Bacterial Multienzyme Complexes Involves Highly Dynamic Protein-Protein Anchors

DOI: 10.1074/jbc.M114.633339 DOI Help
PMID: 25855788 PMID Help

Authors: Kate Cameron (Universitário do Alto da Ajuda) , Shabir Najmudin (Universitário do Alto da Ajuda) , Victor D. Alves (Universitário do Alto da Ajuda) , Edward A. Bayer (The Weizmann Institute of Science) , Steven P. Smith (University, Kingston) , Pedro Bule (Universitário do Alto da Ajuda) , Helen Waller (Newcastle University) , Luís M. A. Ferreira (Universitário do Alto da Ajuda) , Harry J. Gilbert (Newcastle University) , Carlos M. G. A. Fontes (Universitário do Alto da Ajuda)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry , VOL 290 (21) , PAGES 13578 - 13590

State: Published (Approved)
Published: April 2015

Open Access Open Access

Abstract: Protein-protein interactions play a pivotal role in the assembly of the cellulosome, one of nature's most intricate nanomachines dedicated to the depolymerization of complex carbohydrates. The integration of cellulosomal components usually occurs through the binding of type I dockerin modules located at the C terminus of the enzymes to cohesin modules located in the primary scaffoldin subunit. Cellulosomes are typically recruited to the cell surface via type II cohesin-dockerin interactions established between primary and cell-surface anchoring scaffoldin subunits. In contrast with type II interactions, type I dockerins usually display a dual binding mode that may allow increased conformational flexibility during cellulosome assembly. Acetivibrio cellulolyticus produces a highly complex cellulosome comprising an unusual adaptor scaffoldin, ScaB, which mediates the interaction between the primary scaffoldin, ScaA, through type II cohesin-dockerin interactions and the anchoring scaffoldin, ScaC, via type I cohesin-dockerin interactions. Here, we report the crystal structure of the type I ScaB dockerin in complex with a type I ScaC cohesin in two distinct orientations. The data show that the ScaB dockerin displays structural symmetry, reflected by the presence of two essentially identical binding surfaces. The complex interface is more extensive than those observed in other type I complexes, which results in an ultra-high affinity interaction (Ka ∼1012 m). A subset of ScaB dockerin residues was also identified as modulating the specificity of type I cohesin-dockerin interactions in A. cellulolyticus. This report reveals that recruitment of cellulosomes onto the cell surface may involve dockerins presenting a dual binding mode to incorporate additional flexibility into the quaternary structure of highly populated multienzyme complexes.

Journal Keywords: Cell Surface; Cellulase; Cellulose; Cellulosome; Protein-Protein Interaction; Cell-Surface Attachment

Subject Areas: Biology and Bio-materials


Instruments: I03-Macromolecular Crystallography , I04-Macromolecular Crystallography

Added On: 18/11/2015 14:38

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