Shibata T, Nakasu S, Yasui K, Kikuchi A
J Biol Chem. 1987 Aug 5;262(22):10419-21.
Reverse gyrase is a type I DNA topoisomerase that promotes positive supercoiling of closed-circular double-stranded DNA through an ATP-dependent reaction, and it was purified from an archaebacterium, Sulfolobus. When ATP is replaced by UTP, GTP, or CTP, this enzyme just relaxes the negatively supercoiled closed-circular double-stranded DNA. We found that reverse gyrase hydrolyzes ATP through a double-stranded DNA-dependent reaction. The superhelicity of the DNA did not affect the ATPase activity. However, reverse gyrase does not hydrolyze UTP, GTP, or CTP. Therefore, any of the four nucleotide 5'-triphosphates acts as an effector for the topoisomerase activity of reverse gyrase, but only ATP supports the positive supercoiling of closed-circular double-stranded DNA, through the energy released on its hydrolysis. Single-stranded DNA was a much more potent cofactor for the ATPase activity of the enzyme than double-stranded DNA, and it acted as a potent inhibitor for the topoisomerase activity on double-stranded DNA. These results indicate that reverse gyrase has higher affinity to single-stranded DNA than to double-stranded DNA, which suggests a cellular function of the enzyme.
反向回旋酶是一种I型DNA拓扑异构酶，通过依赖ATP的反应促进闭环双链DNA的正超螺旋化，它是从嗜热栖热菌中纯化得到的。当ATP被UTP、GTP或CTP取代时，这种酶只会使负超螺旋闭环双链DNA松弛。我们发现反向回旋酶通过依赖双链DNA的反应水解ATP。DNA的超螺旋状态不影响ATP酶活性。然而，反向回旋酶不水解UTP、GTP或CTP。因此，四种核苷5'-三磷酸中的任何一种都可作为反向回旋酶拓扑异构酶活性的效应物，但只有ATP通过其水解释放的能量支持闭环双链DNA的正超螺旋化。单链DNA作为该酶ATP酶活性的辅助因子比双链DNA更有效，并且它对双链DNA上的拓扑异构酶活性起强效抑制剂的作用。这些结果表明，反向回旋酶对单链DNA的亲和力高于对双链DNA的亲和力，这提示了该酶的细胞功能。
