Tertiary Structure and Characterization of a Glycoside Hydrolase Family 44 Endoglucanase from Clostridium acetobutylicum

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2010-01-01
Authors
Warner, Christopher
Hoy, Julie
Reilly, Peter
Shilling, Taran
Linnen, Michael
Ginder, Nathaniel
Ford, Clark
Honzatko, Richard
Reilly, Peter
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Chemical and Biological Engineering
Abstract

A gene encoding a glycoside hydrolase family 44 (GH44) protein from Clostridium acetobutylicum ATCC 824 was synthesized and transformed into Escherichia coli.The previously uncharacterized protein was expressed with a C-terminal His tag and purified by nickel-nitrilotriacetic acid affinity chromatography. Crystallization and X-ray diffraction to a 2.2-Å resolution revealed a triose phosphate isomerase (TIM) barrel-like structure with additional Greek key and β-sandwich folds, similar to other GH44 crystal structures. The enzyme hydrolyzes cellotetraose and larger cellooligosaccharides, yielding an unbalanced product distribution, including some glucose. It attacks carboxymethylcellulose and xylan at approximately the same rates. Its activity on carboxymethylcellulose is much higher than that of the isolated C. acetobutylicum cellulosome. It also extensively converts lichenan to oligosaccharides of intermediate size and attacks Avicel to a limited extent. The enzyme has an optimal temperature in a 10-min assay of 55°C and an optimal pH of 5.0.

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This is a post-print of an article from Applied and Environmental Microbiology, 76, no. 1 (January 2010): 338–346, doi: 10.1128/AEM.02026-09.

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