期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：19
页码：7293-7298
DOI：10.1073/pnas.0401595101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：DNA gyrase is unique among enzymes for its ability to actively introduce negative supercoils into DNA. This function is mediated in part by the C-terminal domain of its A subunit (GyrA CTD). Here, we report the crystal structure of this {approx}35-kDa domain determined to 1.75-A resolution. The GyrA CTD unexpectedly adopts an unusual fold, which we term a {beta}-pinwheel, that is globally reminiscent of a {beta}-propeller but is built of blades with a previously unobserved topology. A large, conserved basic patch on the outer edge of this domain suggests a likely site for binding and bending DNA; fluorescence resonance energy transfer-based assays show that the GyrA CTD is capable of bending DNA by [IMG]=" BORDER="0">180{degrees} over a 40-bp region. Surprisingly, we find that the CTD of the topoisomerase IV A subunit, which shares limited sequence homology with the GyrA CTD, also bends DNA. Together, these data provide a physical explanation for the ability of DNA gyrase to constrain a positive superhelical DNA wrap, and also suggest that the particular substrate preferences of topoisomerase IV might be dictated in part by the function of this domain.
