Molecular structural basis for the cold-adaptedness of psychrophilic beta-glucosidase BglU in Micrococcus antarcticus----中国科学院微生物研究所

科研成果

论文题目:	Molecular structural basis for the cold-adaptedness of psychrophilic beta-glucosidase BglU in Micrococcus antarcticus
作者:	Miao Li-Li, Hou Yan-Jie, Fan Hong-Xia, Qu Jie, Qi Chao, Liu Ying, Li De-Feng, and Liu Zhi-Pei.
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刊物名称:	Appl Environ Microbiol
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年份:	2016
影响因子:	4.359
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摘要:	Psychrophilic enzymes play crucial roles in cold adaptation of microbes, and provide useful models for studies of protein evolution, folding, and dynamic properties. We examined the crystal structure (2.2 A resolution) of the psychrophilic beta-glucosidase BglU, a member of the GH1 enzyme family found in the cold-adapted bacterium Micrococcus antarcticus. Structural comparison and sequence alignment between BglU and its mesophilic and thermophilic counterpart enzymes (BglB and GlyTn, respectively), revealed two notable features distinct to BglU: a unique long-loop L3 (35 vs. 7 amino acids in others) involved in substrate binding; a unique amino acids His299 (Tyr in others) involved in stabilization of an ordered water molecule chain. Shortening of loop L3 to 25 amino acids reduced low-temperature catalytic activity, substrate-binding ability, optimal temperature, and Tm. Mutation of His299 to Tyr increased optimal temperature, Tm, and catalytic activity. Conversely, mutation of Tyr301 to His in BglB caused reduction of catalytic activity, thermostability, and optimal temperature (45 to 35 degrees C). Loop L3 shortening and H299Y substitution jointly restored enzyme activity to the level of BglU, but at moderate temperatures. Our findings indicate that loop L3 controls the level of catalytic activity at low temperatures, residue His299 is responsible for thermolability (particularly heat lability of the active center), and long-loop L3 and His299 are jointly responsible for the psychrophilic properties. The described structural basis for the cold-adaptedness of BglU will be helpful for structure-based engineering of new cold-adapted enzymes, and for production of mutants useful in variety of industrial processes at different temperatures.