Structure of the catalytic domain of the Clostridium thermocellum cellulase CelT
Cellulases hydrolyze cellulose, a major component of plant cell walls, to oligosaccharides and monosaccharides. Several Clostridium species secrete multi‐enzyme complexes (cellulosomes) containing cellulases. C. thermocellum CelT, a family 9 cellulase, lacks the accessory module(s) necessary for activity, unlike most other family 9 cellulases. Therefore, characterization of the CelT structure is essential in order to understand its catalytic mechanism. Here, the crystal structure of free CelTΔdoc, the catalytic domain of CelT, is reported at 2.1 Å resolution. Its structure differs in several aspects from those of other family 9 cellulases. CelTΔdoc contains an additional α‐helix, α‐helices of increased length and two additional surface‐exposed β‐strands. It also contains three calcium ions instead of one as found in C. cellulolyticum Cel9M. CelTΔdoc also has two flexible loops at the open end of its active‐site cleft. Movement of these loops probably allows the substrate to access the active site. CelT is stable over a wide range of pH and temperature conditions, suggesting that CelT could be used to convert cellulose biomass into biofuel.
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Document Type: Research Article
Publication date: 2012-03-01