title: Crystal structure of β-N-acetylglucosaminidase CbsA from Thermotoga neapolitana.
abstract: CbsA from the thermophilic marine bacteria Thermotoga neapolitana is a chitinolyitc enzyme that can cleave a glycosidic bond of the polymer N-acetylglucosamine at the non-reducing end. This enzyme has particularly high activity on di-N-acetylchitobiose. CbsA consists of a family of 3 glycoside hydrolase (GH3)-type catalytic domains and a unique C-terminal domain. The C-terminal domain distinguishes CbsA from other GH3-type enzymes. Sequence analyses have suggested that CbsA has the Asp-His dyad as a general acid/base with the NagZ of Bacillus subtilis and the Salmonella enterica serovar Typhimurium. Here, we determined the crystal structure of CbsA from T. neapolitana at a resolution of 2.0 Å using the Zn-SAD method, revealing a unique homodimeric assembly facilitated by the C-terminal domains in the dimer. We observed that CbsA is strongly inhibited by ZnCl2, and two zinc ions were consistently bound in the active site. Our results can explain the zinc ion's inhibition mechanism in the subfamily of GH3 enzymes, and provide information on the structural diversity and substrate specificity of this hydrolase family.
authors.affiliation: Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jin-Sik
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Institute of Fisheries Sciences, Pukyong National University, Busan, Republic of Korea.
authors.forename: Bo-Young
authors.initials: BY
authors.lastname: Yoon
authors.affiliation: Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jinsook
authors.initials: J
authors.lastname: Ahn
authors.affiliation: Department of Microbiology, College of Natural Sciences, Pusan National University, Busan, Republic of Korea.
authors.forename: Jaeho
authors.initials: J
authors.lastname: Cha
authors.affiliation: Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul, Republic of Korea. Electronic address: hanc210@snu.ac.kr.
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
mesh_terms: D000118:Acetylglucosaminidase / Q000737:chemistry* / Q000378:metabolism*; D001412:Bacillus subtilis / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D011487:Protein Conformation; D055503:Protein Multimerization; D012486:Salmonella typhimurium / Q000201:enzymology; D013379:Substrate Specificity; D046949:Thermotoga neapolitana / Q000201:enzymology*; D015032:Zinc / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D000118:Acetylglucosaminidase; D015032:Zinc
keywords: Crystal structure; Thermostable enzyme; Thermotoga; cbsA; β-N-Acetylglucosaminidase