TY - JOUR
T1 - Structural insights into a unique cellulase fold and mechanism of cellulose hydrolysis
AU - Brás, Joana L. A.
AU - Cartmell, Alan
AU - Carvalho, Ana Luísa M.
AU - Verzé, Genny
AU - Bayer, Edward A.
AU - Vazana, Yael
AU - Correia, Márcia A. S.
AU - Prates, José A. M.
AU - Ratnaparkhe, Supriya
AU - Boraston, Alisdair B.
AU - Romão, Maria J.
AU - Fontes, Carlos M. G. A.
AU - Gilbert, Harry J.
N1 - The authors acknowledge financial support from Fundacao para a Ciencia e a Tecnologia, Portugal, through grants PTDC/BIA-PRO/69732/2006, PTDC/QUI-BIQ/100359/2008, and the individual fellowship SFRH/BD/38667/2007 (to J.L.A.B.); the U.K. Biological and Biotechnological Sciences Research Council (studentship to A. C.); the US Department of Energy (Grant 00562492); and the Israel Science Foundation (Grant 966/09). The authors also acknowledge the European Synchrotron Radiation Facility, Grenoble, France (beamline ID14-EH4) for access and technical support during data collection.
PY - 2011/3/29
Y1 - 2011/3/29
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=79955116598&partnerID=8YFLogxK
U2 - 10.1073/pnas.1015006108
DO - 10.1073/pnas.1015006108
M3 - Article
C2 - 21393568
AN - SCOPUS:79955116598
VL - 108
SP - 5237
EP - 5242
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 13
ER -