2004年10月22日
Crystal structure of family GH-8 chitosanase with subclass II specificity from Bacillus sp. K17.
Journal of molecular biology
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- 巻
- 343
- 号
- 3
- 開始ページ
- 785
- 終了ページ
- 95
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1016/j.jmb.2004.08.028
- 出版者・発行元
- ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Crystal structures of chitosanase from Bacillus sp. K17 (ChoK) have been determined at 1.5 A resolution in the active form and at 2.0 A resolution in the inactive form. This enzyme belongs to the family GH-8, out of 93 glycoside hydrolase families, and exhibits the substrate specificity of subclass II chitosanase. The catalytic site is constructed on the scaffold of a double-alpha(6)/alpha(6)-barrel, which is formed by six repeating helix-loop-helix motifs. This structure is quite different from those of the GH-46 chitosanases and of GH-5. Structural comparison with CelA (a cellulase belonging to the same family GH-8) suggests that the proton donor Glu122 is conserved, but the proton acceptor is the inserted Glu309 residue, and that the corresponding Asp278 residue in CelA is inactivated in ChoK. The four acidic residues, Asp179, Glu309, Asp183 and Glu107, can be involved in substrate recognition through interactions with the amino groups of the glucosamine residues bound in the -3, -2, -1 and +1 sites, respectively. The hydrophobic Trp235, Trp166, Phe413 and Tyr318 residues are highly conserved for binding of the hexose rings at the -3, -2, +1 and +2 sites, respectively. These structural features indicate that enzymes in GH-8 can be further divided into three subfamilies. Different types of chitosanases are discussed in terms of convergent evolution from different structural ancestors.
- リンク情報
- ID情報
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- DOI : 10.1016/j.jmb.2004.08.028
- ISSN : 0022-2836
- PubMed ID : 15465062
- Web of Science ID : WOS:000224503300021