Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, D-48149 Muenster, Germany.
Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):14085-90. doi: 10.1073/pnas.1102100108. Epub 2011 Aug 4.
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.
DNA 回旋酶在 ATP 依赖的反应中将负超螺旋引入 DNA 中。DNA 超螺旋的催化通过链穿越机制进行，其中 DNA 的 T 片段穿过短暂切割的 G 片段中的间隙。链穿越需要回旋酶中三个蛋白质界面的协调关闭和打开，即 N 门、DNA 门和 C 门。我们在这里表明，DNA 与回旋酶的 DNA 门结合以及 DNA 围绕 GyrA 的 C 末端结构域的缠绕导致 N 门变窄。这种半关闭状态为在上部腔室中捕获 T 片段做好准备。随后，在结合 ATP 时 N 门关闭，使反应向链穿越方向推进。ATP 水解后 N 门重新打开，允许进一步的催化循环。DNA 结合、切割和缠绕以及 N 门变窄是密切相关的事件，它们协调 DNA 和 N 门的构象变化。
