Jankowsky E, Gross C H, Shuman S, Pyle A M
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
Nature. 2000 Jan 27;403(6768):447-51. doi: 10.1038/35000239.
All aspects of cellular RNA metabolism and processing involve DExH/D proteins, which are a family of enzymes that unwind or manipulate RNA in an ATP-dependent fashion. DExH/D proteins are also essential for the replication of many viruses, and therefore provide targets for the development of therapeutics. All DExH/D proteins characterized to date hydrolyse nucleoside triphosphates and, in most cases, this activity is stimulated by the addition of RNA or DNA. Several members of the family unwind RNA duplexes in an NTP-dependent fashion in vitro; therefore it has been proposed that DExH/D proteins couple NTP hydrolysis to RNA conformational change in complex macromolecular assemblies. Despite the central role of DExH/D proteins, their mechanism of RNA helicase activity remains unknown. Here we show that the DExH protein NPH-II unwinds RNA duplexes in a processive, unidirectional fashion with a step size of roughly one-half helix turn. We show that there is a quantitative connection between ATP utilization and helicase processivity, thereby providing direct evidence that DExH/D proteins can function as molecular motors on RNA.
细胞RNA代谢和加工的各个方面都涉及DExH/D蛋白，这是一类以ATP依赖方式解开或操控RNA的酶家族。DExH/D蛋白对许多病毒的复制也至关重要，因此为治疗药物的开发提供了靶点。迄今为止鉴定出的所有DExH/D蛋白都能水解核苷三磷酸，而且在大多数情况下，RNA或DNA的添加会刺激这种活性。该家族的几个成员在体外以NTP依赖方式解开RNA双链体；因此有人提出，DExH/D蛋白在复杂的大分子组装中将NTP水解与RNA构象变化联系起来。尽管DExH/D蛋白具有核心作用，但其RNA解旋酶活性的机制仍然未知。在这里，我们表明DExH蛋白NPH-II以连续、单向的方式解开RNA双链体，步长约为半个螺旋圈。我们表明，ATP利用与解旋酶持续性之间存在定量联系，从而提供了直接证据，证明DExH/D蛋白可以在RNA上充当分子马达。
