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核糖核酸酶H
立体化学
蛋白质二级结构
生物物理学
生物化学
作者
Jozef Sevcik,Lubica Urbanikova,Zbigniew Dauter,Keith S. Wilson
出处
期刊:Acta Crystallographica Section D-biological Crystallography
[International Union of Crystallography]
日期:1998-09-01
卷期号:54 (5): 954-963
被引量:31
标识
DOI:10.1107/s0907444998004429
摘要
We report the 1.7 A resolution structure of RNase Sa complexed with the polypeptide inhibitor barstar. The crystals are in the hexagonal space group P65 with unit-cell dimensions a = b = 56.9, c = 135.8 A and the asymmetric unit contains one molecule of the complex. RNase Sa is an extracellular microbial ribonuclease produced by Streptomyces aureofaciens. Barstar is the natural inhibitor of barnase, the ribonuclease of Bacillus amyloliquefaciens. It inhibits RNase Sa and barnase in a similar manner by steric blocking of the active site. The structure of RNase Sa is very similar to that observed in crystals of the native enzyme and its complexes with nucleotides. Barstar retains the structure found in its complex with barnase. The accessible surface area of protein buried in the complex is about 300 A2 smaller and there are fewer hydrogen bonds in the enzyme-inhibitor interface in RNase Sa-barstar than in barnase-barstar, providing an explanation of the reduced binding affinity in the former. Previous studies of barstar complexes have used mutants of the inhibitor and this is the first structure which includes wild-type barstar.
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