Journal
BIOTECHNOLOGY AND BIOENGINEERING
Volume 110, Issue 12, Pages 3093-3103Publisher
WILEY
DOI: 10.1002/bit.24982
Keywords
xylanase; glycoside hydrolase; bacterial Ig-like domain; crystal structure; intimin; bacterium; termite gut
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Funding
- Knowledge Innovation Program of the Chinese Academy of Sciences [KSCX2-EW-G-13-1]
- National Basic Research Program of China (973 Program) [2011CB707403]
- National Natural Science Foundation of China [30900150, 31172153]
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Bacterial Ig-like (Big) domains are commonly distributed in glycoside hydrolases (GH), but their structure and function remains undefined. Xylanase is a GH, and catalyzes the hydrolysis of the internal -xylosidic linkages of xylan. In this study, we report the molecular cloning, biochemical and biophysical characterization, and crystal structure of a termite gut bacterial xylanase, Xyl-ORF19, which was derived from gut bacteria of a wood-feeding termite (Globitermes brachycerastes). The protein architecture of Xyl-ORF19 reveals that it has two domains, a C-terminal GH10 catalytic domain and an N-terminal Big_2 non-catalytic domain. The catalytic domain folds in an (/)(8) barrel as most GH10 xylanases do, but it has two extra -strands. The non-catalytic domain is structurally similar to an immunoglobulin-like domain of intimins. The recombinant enzyme without the non-catalytic domain has fairly low catalytic activity, and is different from the full-length enzyme in kinetic parameters, pH and temperature profiles, which suggests the non-catalytic domain could affect the enzyme biochemical and biophysical properties as well as the role for enzyme localization. This study provides a molecular basis for future efforts in xylanase bioengineering. Biotechnol. Bioeng. 2013;110: 3093-3103. (c) 2013 Wiley Periodicals, Inc.
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