Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 280, Issue 28, Pages 26177-26184Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M502838200
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Funding
- NCRR NIH HHS [RR-01646] Funding Source: Medline
- NIGMS NIH HHS [GM51330, T32 GM007598, R01 GM044853] Funding Source: Medline
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DNA gyrase is unique among type II topoisomerases in that its DNA supercoiling activity is unidirectional. The C-terminal domain of the gyrase A subunit (GyrA-CTD) is required for this supercoiling bias. We report here the x-ray structure of the Escherichia coli GyrA-CTD ( Protein Data Bank code 1ZI0). The E. coli GyrA-CTD adopts a circular-shaped beta-pinwheel fold first seen in the Borrelia burgdorferi GyrA-CTD. However, whereas the B. burgdorferi GyrA-CTD is flat, the E. coli GyrA-CTD is spiral. DNA relaxation assays reveal that the E. coli GyrA-CTD wraps DNA inducing substantial (+) super-helicity, while the B. burgdorferi GyrA-CTD introduces a more modest (+) superhelicity. The observation of a superhelical spiral in the present structure and that of the Bacillus stearothermophilus ParC-CTD structure suggests unexpected similarities in substrate selectivity between gyrase and Topo IV enzymes. We propose a model wherein the right-handed ((+) solenoidal) wrapping of DNA around the E. coli GyrA-CTD enforces unidirectional (+) DNA supercoiling.
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