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The GyrA-box determines the geometry of DNA bound to gyrase and couples DNA binding to the nucleotide cycle
Authors:Martin A. Lanz  Dagmar Klostermeier
Affiliation:Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, D-48149 Muenster, Germany
Abstract:DNA gyrase catalyses the adenosine triphosphate-dependent introduction of negativesupercoils into DNA. The enzyme binds a DNA-segment at the so-called DNA-gate and cleavesboth DNA strands. DNA extending from the DNA-gate is bound at the perimeter of thecylindrical C-terminal domains (CTDs) of the GyrA subunit. The CTDs are believed tocontribute to the wrapping of DNA around gyrase in a positive node as a prerequisite forstrand passage towards negative supercoiling. A conserved seven amino acid sequence motifin the CTD, the so-called GyrA-box, has been identified as a hallmark feature of gyrases.Mutations of the GyrA-box abolish supercoiling. We show here that the GyrA-box marginallystabilizes the CTDs. Although it does not contribute to DNA binding, it is required forDNA bending and wrapping, and it determines the geometry of the bound DNA. Mutations ofthe GyrA-box abrogate a DNA-induced conformational change of the gyrase N-gate anduncouple DNA binding and adenosine triphosphate hydrolysis. Our results implicate theGyrA-box in coordinating DNA binding and the nucleotide cycle.
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