Reverse gyrase is a unique type I topoisomerase that catalyzes the introduction of positive supercoils into DNA in an ATP-dependent reaction. Supercoiling is the result of a functional cooperation of the N-terminal helicase domain with the C-terminal topoisomerase domain. The helicase domain is a nucleotide-dependent conformational switch that alternates between open and closed states with different affinities for single- and double-stranded DNA. The isolated helicase domain as well as full-length reverse gyrase can transiently unwind double-stranded regions in an ATP-dependent reaction. The latch region of reverse gyrase, an insertion into the helicase domain with little conservation in sequence and length, has been proposed to coordinate events in the helicase domain with strand passage by the topoisomerase domain. Latch deletions lead to a reduction in or complete loss of supercoiling activity. Here we show that the latch consists of two functional parts, a globular domain that is dispensable for DNA supercoiling and a β-hairpin that connects the globular domain to the helicase domain and is required for supercoiling activity. The β-hairpin thus constitutes a minimal latch that couples ATP-dependent processes in the helicase domain to DNA processing by the topoisomerase domain.

反向旋旋酶是一种独特的I型拓扑异构酶，可在ATP依赖性反应中催化将阳性超螺旋引入DNA中。超螺旋是N-末端解旋酶结构域与C-末端拓扑异构酶结构域功能性合作的结果。解旋酶结构域是核苷酸依赖性的构象开关，其在打开状态和关闭状态之间交替，对单链和双链DNA具有不同的亲和力。分离的解旋酶结构域以及全长反向旋旋酶可以在依赖于ATP的反应中暂时解开双链区。已经提出了反向回旋酶的闩锁区，其在解旋酶结构域中的插入，其序列和长度几乎没有保守性，以协调解旋酶结构域中的事件以及拓扑异构酶结构域的链传递。闩锁缺失导致超螺旋活性的降低或完全丧失。在这里，我们显示闩锁由两个功能部分组成，一个球形域对于DNA超螺旋是可有可无的，一个β型发夹将球形域与解旋酶域连接起来，并且是超螺旋活性所必需的。因此，β-发夹构成了最小的闩锁，该闩锁将解旋酶域中的ATP依赖性过程与拓扑异构酶域的DNA处理耦合在一起。