2vn5

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Revision as of 18:41, 22 May 2008

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Template:STRUCTURE 2vn5

THE CLOSTRIDIUM CELLULOLYTICUM DOCKERIN DISPLAYS A DUAL BINDING MODE FOR ITS COHESIN PARTNER

Overview

The plant cell wall degrading apparatus of anaerobic bacteria comprises a large multi-enzyme complex termed the "cellulosome". The complex assembles through the interaction of enzyme-derived dockerin modules with the multiple cohesin modules of the non-catalytic scaffolding protein. Here we report the crystal structure of the C. cellulolyticum cohesin-dockerin complex in both possible orientations. The data show that the dockerin displays structural symmetry reflected by the presence of two essentially identical cohesin binding surfaces. In one binding mode, visualised through the A16S/L17T dockerin mutant, the C-terminal helix makes extensive interactions with its cohesin partner. In the other binding mode observed through the A47S/F48T dockerin variant, the dockerin is reorientated by 180o, and interacts with the cohesin primarily through the N-terminal helix. Apolar interactions dominate cohesin-dockerin recognition which is centred around a hydrophobic pocket on the surface of the cohesin, formed by Leu-87 and Leu-89, which is occupied, in the two binding modes, by the dockerin residues Phe-19 and Leu-50, respectively. Despite the structural similarity between the C. cellulolyticum and C. thermocellum cohesins and dockerins there is no cross-specificity between the protein partners from the two organisms. The crystal structure of the C. cellulolyticum complex shows that organism-specific recognition between the protomers is dictated by apolar interactions primarily between only two residues, Leu-17 in the dockerin and the cohesin amino acid Ala-129. The biological significance of the plasticity in dockerin-cohesin recognition, observed here in C. cellulolyticum, and reported previously in C. thermocellum, is discussed.

About this Structure

2VN5 is a Protein complex structure of sequences from Clostridium cellulolyticum. Full crystallographic information is available from OCA.

Reference

The clostridium cellulolyticum dockerin displays a dual binding mode for its cohesin partner., Pinheiro BA, Proctor MR, Martinez-Fleites C, Prates JA, Money VA, Davies GJ, Bayer EA, Fontes CM, Fierobe HP, Gilbert HJ, J Biol Chem. 2008 Apr 28;. PMID:18445585 Page seeded by OCA on Thu May 22 21:41:02 2008