title: The crystal structure of the endoglucanase Cel10, a family 8 glycosyl hydrolase from Klebsiella pneumoniae.
abstract: Cellulases are produced by microorganisms that grow on cellulose biomass. Here, a cellulase, Cel10, was identified in a strain of Klebsiella pneumoniae isolated from Chinese bamboo rat gut. Analysis of substrate specificity showed that Cel10 is able to hydrolyze amorphous carboxymethyl cellulose (CMC) and crystalline forms of cellulose (Avicel and xylan) but is unable to hydrolyze p-nitrophenol β-D-glucopyranoside (p-NPG), proving that Cel10 is an endoglucanase. A phylogenetic tree analysis indicates that Cel10 belongs to the glycoside hydrolase 8 (GH8) subfamily. In order to further understanding of its substrate specificity, the structure of Cel10 was solved by molecular replacement and refined to 1.76 Å resolution. The overall fold is distinct from those of most other enzymes belonging to the GH8 subfamily. Although it forms the typical (α/α)6-barrel motif fold, like Acetobacterxylinum CMCax, one helix is missing. Structural comparisons with Clostridium thermocellum CelA (CtCelA), the best characterized GH8 endoglucanase, revealed that sugar-recognition subsite -3 is completely missing in Cel10. The absence of this subsite correlates to a more open substrate-binding cleft on the cellooligosaccharide reducing-end side.
authors.affiliation: Key Laboratory for Integrated Chinese Traditional and Western Veterinary Medicine and Animal Healthcare, College of Animal Science, Fujian Agriculture and Forestry University, 15 Shang Xia Dian Road, Fuzhou 350002, People's Republic of China.
authors.forename: Ayman
authors.initials: A
authors.lastname: Attigani
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 West Yangqiao Road, Fuzhou 350002, People's Republic of China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 West Yangqiao Road, Fuzhou 350002, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 West Yangqiao Road, Fuzhou 350002, People's Republic of China.
authors.forename: Yadan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Key Laboratory for Integrated Chinese Traditional and Western Veterinary Medicine and Animal Healthcare, College of Animal Science, Fujian Agriculture and Forestry University, 15 Shang Xia Dian Road, Fuzhou 350002, People's Republic of China.
authors.forename: Dingping
authors.initials: D
authors.lastname: Bai
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 West Yangqiao Road, Fuzhou 350002, People's Republic of China.
authors.forename: Shengping
authors.initials: S
authors.lastname: Li
authors.affiliation: Key Laboratory for Integrated Chinese Traditional and Western Veterinary Medicine and Animal Healthcare, College of Animal Science, Fujian Agriculture and Forestry University, 15 Shang Xia Dian Road, Fuzhou 350002, People's Republic of China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Huang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry* / Q000378:metabolism; D002480:Cellulase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002482:Cellulose / Q000737:chemistry* / Q000378:metabolism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D007711:Klebsiella pneumoniae / Q000737:chemistry* / Q000145:classification / Q000201:enzymology; D008958:Models, Molecular; D010802:Phylogeny; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D017510:Protein Folding; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D013379:Substrate Specificity; D014990:Xylans / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D014990:Xylans; D002482:Cellulose; D002480:Cellulase; D002266:Carboxymethylcellulose Sodium
keywords: Cel10; Klebsiella pneumoniae; carboxymethyl cellulase; cellulases; cellulose biosynthesis; crystal structure