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Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):14085-90. doi: 10.1073/pnas.1102100108. Epub 2011 Aug 4.

DNA-induced narrowing of the gyrase N-gate coordinates T-segment capture and strand passage.

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Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, D-48149 Muenster, Germany.


DNA gyrase introduces negative supercoils into DNA in an ATP-dependent reaction. DNA supercoiling is catalyzed by a strand-passage mechanism, in which a T-segment of DNA is passed through the gap in a transiently cleaved G-segment. Strand passage requires the coordinated closing and opening of three protein interfaces in gyrase, the N-gate, DNA-gate, and C-gate. We show here that DNA binding to the DNA-gate of gyrase and wrapping of DNA around the C-terminal domains of GyrA induces a narrowing of the N-gate. This half-closed state prepares capture of a T-segment in the upper cavity of gyrase. Subsequent N-gate closure upon binding of ATP then poises the reaction toward strand passage. The N-gate reopens after ATP hydrolysis, allowing for further catalytic cycles. DNA binding, cleavage, and wrapping and N-gate narrowing are intimately linked events that coordinate conformational changes at the DNA and the N-gate.

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