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

DOI: 10.1073/pnas.1015006108 DOI Help

Authors: J. L. A. Bras (Universidade Técnica de Lisboa) , A. Cartmell (University of Georgia) , A. L. M. Carvalho (Universidade Nova de Lisbo) , G. Verze (Universidade Nova de Lisbo) , E. A. Bayer (The Weizmann Institute of Science) , Y. Vazana (The Weizmann Institute of Science) , M. A. S. Correia (Universidade Técnica de Lisboa) , J. A. M. Prates (Universidade Técnica de Lisboa) , S. Ratnaparkhe (University of Georgia) , A. B. Boraston (University of Victoria) , M. J. Romao (Universidade Nova de Lisbo) , C. M. G. A. Fontes (Universidade Técnica de Lisboa) , H. J. Gilbert (University of Georgia)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 108 (13) , PAGES 5237 - 5242

State: Published (Approved)
Published: March 2011

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.

Journal Keywords: Biofuels; glycoside hydrolases

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography

Other Facilities: ESRF

Added On: 11/02/2016 15:03

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