Open AccessPurification, crystallization and preliminary X‐ray characterization of the pentamodular arabinoxylanase Ct Xyl5A from Clostridium thermocellum
Author(s) -
Brás Joana L. A.,
Correia Márcia A. S.,
Romão Maria J.,
Prates José A. M.,
Fontes Carlos M. G. A.,
Najmudin Shabir
Publication year - 2011
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309111020823
Subject(s) - cellulosome , clostridium thermocellum , xylanase , glycoside hydrolase , cellulase , chemistry , biochemistry , protein data bank (rcsb pdb) , thermophile , hydrolase , enzyme
The cellulosome, a highly elaborate extracellular multi‐enzyme complex of cellulases and hemicellulases, is responsible for the degradation of plant cell walls. The xylanase Ct Xyl5A (Cthe_2193) is a multimodular arabinoxylanase which is one of the largest components of the Clostridium thermocellum cellulosome. The N‐terminal catalytic domain of Ct Xyl5A, which is a member of glycoside hydrolase family 5 (GH5), is responsible for the hydrolysis of arabinoxylans. Appended after it are three noncatalytic carbohydrate‐binding modules (CBMs), which belong to families 6 (CBM6), 13 (CBM13) and 62 (CBM62). In addition, Ct Xyl5A has a fibronectin type III‐like (Fn3) module preceding the CBM62 and a type I dockerin (DOK) module following it which allows the enzyme to be integrated into the cellulosome through binding to a cohesin module of the protein scaffold CipA. Crystals of the pentamodular enzyme without the DOK module at the C‐terminus, with the domain architecture Ct GH5‐CBM6‐CBM13‐Fn3‐CBM62, have been obtained. The structure of this pentamodular xylanase has been determined by molecular replacement to a resolution of 2.64 Å using coordinates of Ct GH5‐CBM6, Fn3 and CBM62 from the PDB as search models.