Structural insights into a unique cellulase fold and mechanism of cellulose hydrolysis



Bras, Joana LA, Cartmell, Alan ORCID: 0000-0002-5512-249X, Carvalho, Ana Luisa M, Verze, Genny, Bayer, Edward A, Vazana, Yael, Correia, Marcia AS, Prates, Jose AM, Ratnaparkhe, Supriya, Boraston, Alisdair B
et al (show 3 more authors) (2011) Structural insights into a unique cellulase fold and mechanism of cellulose hydrolysis. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 108 (13). pp. 5237-5242.

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Abstract

Clostridium thermocellum is a well-characterized cellulose-degrading microorganism. The genome sequence of C. thermocellum encodes a number of proteins that contain type I dockerin domains, which implies that they are components of the cellulose-degrading apparatus, but display no significant sequence similarity to known plant cell wall-degrading enzymes. Here, we report the biochemical properties and crystal structure of one of these proteins, designated CtCel124. The protein was shown to be an endo-acting cellulase that displays a single displacement mechanism and acts in synergy with Cel48S, the major cellulosomal exo-cellulase. The crystal structure of CtCel124 in complex with two cellotriose molecules, determined to 1.5 Å, displays a superhelical fold in which a constellation of α-helices encircle a central helix that houses the catalytic apparatus. The catalytic acid, Glu96, is located at the C-terminus of the central helix, but there is no candidate catalytic base. The substrate-binding cleft can be divided into two discrete topographical domains in which the bound cellotriose molecules display twisted and linear conformations, respectively, suggesting that the enzyme may target the interface between crystalline and disordered regions of cellulose.

Item Type: Article
Uncontrolled Keywords: Clostridium thermocellum, Cellulose, Cellulase, Oligosaccharides, Crystallography, X-Ray, Molecular Structure, Catalytic Domain, Carbohydrate Sequence, Protein Structure, Secondary, Protein Structure, Tertiary, Models, Molecular, Molecular Sequence Data
Depositing User: Symplectic Admin
Date Deposited: 10 Sep 2019 15:35
Last Modified: 30 May 2023 15:33
DOI: 10.1073/pnas.1015006108
Open Access URL: https://www.pnas.org/content/pnas/108/13/5237.full...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3054150