Crystal structures of the laminarinase catalytic domain from Thermotoga maritima MSB8 in complex with inhibitors: Essential residues for β-1,3- and β-1,4-glucan selection

Wen Yih Jeng, Nai Chen Wang, Cheng Tse Lin, Lie Fen Shyur, Andrew H.J. Wang

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27 引文 斯高帕斯(Scopus)

摘要

Laminarinases hydrolyzing the β-1,3-linkage of glucans play essential roles in microbial saccharide degradation. Here we report the crystal structures at 1.65-1.82 Å resolution of the catalytic domain of laminarinase from the thermophile Thermotoga maritima with various space groups in the ligand-free form or in the presence of inhibitors gluconolactone and cetyltrimethylammonium. Ligands were bound at the cleft of the active site near an enclosure formed by Trp-232 and a flexible GASIG loop. A closed configuration at the active site cleft was observed in some molecules. The loop flexibility in the enzyme may contribute to the regulation of endo- or exo-activity of the enzyme and a preference to release laminaritrioses in long chain carbohydrate hydrolysis. Glu-137 and Glu-132 are proposed to serve as the proton donor and nucleophile, respectively, in the retaining catalysis of hydrolyzation. Calcium ions in the crystallization media are found to accelerate crystal growth. Comparison of laminarinase and endoglucanase structures revealed the subtle difference of key residues in the active site for the selection of β-1,3-glucan and β-1,4-glucan substrates, respectively. Arg-85 may be pivotal to β-1,3-glucan substrate selection. The similarity of the structures between the laminarinase catalytic domain and its carbohydrate-binding modules may have evolutionary relevance because of the similarities in their folds.

原文英語
頁(從 - 到)45030-45040
頁數11
期刊Journal of Biological Chemistry
286
發行號52
DOIs
出版狀態已發佈 - 12月 30 2011
對外發佈

ASJC Scopus subject areas

  • 生物化學
  • 分子生物學
  • 細胞生物學

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