title: Structure of the catalytic domain of the Clostridium thermocellum cellulase CelT.
abstract: 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.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Muppuru M
authors.initials: MM
authors.lastname: Kesavulu
authors.forename: Jia Yin
authors.initials: JY
authors.lastname: Tsai
authors.forename: Hsiao Lin
authors.initials: HL
authors.lastname: Lee
authors.forename: Po Huang
authors.initials: PH
authors.lastname: Liang
authors.forename: Chwan Deng
authors.initials: CD
authors.lastname: Hsiao
mesh_terms: D001665:Binding Sites; D020134:Catalytic Domain; D002480:Cellulase / Q000737:chemistry* / Q000378:metabolism; D044603:Cellulosomes / Q000201:enzymology*; D048013:Acetivibrio thermocellus / Q000201:enzymology*; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D006026:Glycoside Hydrolases; D002480:Cellulase