Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 101, Issue 19, Pages 7293-7298Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0401595101
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- NCI NIH HHS [CA 77373, R01 CA077373] Funding Source: Medline
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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 approximate to35-kDa domain determined to 1.75-Angstrom 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 greater than or equal to180degrees 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.
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