title: Structural Insight of a Trimodular Halophilic Cellulase with a Family 46 Carbohydrate-Binding Module.
abstract: Cellulases are the key enzymes used in the biofuel industry. A typical cellulase contains a catalytic domain connected to a carbohydrate-binding module (CBM) through a flexible linker. Here we report the structure of an atypical trimodular cellulase which harbors a catalytic domain, a CBM46 domain and a rigid CBM_X domain between them. The catalytic domain shows the features of GH5 family, while the CBM46 domain has a sandwich-like structure. The catalytic domain and the CBM46 domain form an extended substrate binding cleft, within which several tryptophan residues are well exposed. Mutagenesis assays indicate that these residues are essential for the enzymatic activities. Gel affinity electrophoresis shows that these tryptophan residues are involved in the polysaccharide substrate binding. Also, electrostatic potential analysis indicates that almost the entire solvent accessible surface of CelB is negatively charged, which is consistent with the halophilic nature of this enzyme.
authors.affiliation: Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Huaidong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.|Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Science, Hubei University, Wuhan, China.
authors.forename: Guimin
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Chaoxiang
authors.initials: C
authors.lastname: Yao
authors.affiliation: Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Junaid
authors.affiliation: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, College of Life Science, Hubei University, Wuhan, China.
authors.forename: Zhenghui
authors.initials: Z
authors.lastname: Lu
authors.affiliation: Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.|Key Laboratory of Molecular Biophysics, Ministry of Education, Wuhan, Hubei, China.
authors.forename: Houjin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yanhe
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002241:Carbohydrates / Q000737:chemistry; D020134:Catalytic Domain; D002480:Cellulase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013379:Substrate Specificity; D013499:Surface Properties
chemical_list: D001426:Bacterial Proteins; D002241:Carbohydrates; C109965:CelB endoglucanase; D002480:Cellulase