Rössler O G, Straka A, Stahl H
Medizinische Biochemie und Molekularbiologie, Universität des Saarlandes, D-66421 Homburg, Germany.
Nucleic Acids Res. 2001 May 15;29(10):2088-96. doi: 10.1093/nar/29.10.2088.
RNA helicases, like their DNA-specific counterparts, can function as processive enzymes, unwinding RNA with a defined step size in a unidirectional fashion. Recombinant nuclear DEAD-box protein p68 and its close relative p72 are reported here to function in a similar fashion, though the processivity of both RNA helicases appears to be limited to only a few consecutive catalytic steps. The two proteins resemble each other also with regard to other biochemical properties. We have found that both proteins exhibit an RNA annealing in addition to their helicase activity. By using both these activities the enzymes are able in vitro to catalyse rearrangements of RNA secondary structures that otherwise are too stable to be resolved by their low processive helicase activities. RNA rearrangement proceeds via protein induced formation and subsequent resolution of RNA branch migration structures, whereby the latter step is dependent on ATP hydrolysis. The analysed DEAD-box proteins are reminiscent of certain DNA helicases, for example those found in bacteriophages T4 and T7, that catalyse homologous DNA strand exchange in cooperation with the annealing activity of specific single strand binding proteins.
RNA解旋酶与其作用于DNA的对应物一样，可作为进行性酶发挥作用，以单向方式以确定的步长解开RNA。本文报道重组核DEAD盒蛋白p68及其近亲p72以类似方式发挥作用，尽管这两种RNA解旋酶的进行性似乎仅限于少数连续的催化步骤。这两种蛋白质在其他生化特性方面也彼此相似。我们发现这两种蛋白质除了解旋酶活性外还表现出RNA退火活性。通过利用这两种活性，这些酶在体外能够催化RNA二级结构的重排，否则这些结构因解旋酶活性低且进行性有限而过于稳定难以解析。RNA重排通过蛋白质诱导形成RNA分支迁移结构并随后将其解析来进行，其中后一步骤依赖于ATP水解。所分析的DEAD盒蛋白让人联想到某些DNA解旋酶，例如在噬菌体T4和T7中发现的那些，它们与特定单链结合蛋白的退火活性协同催化同源DNA链交换。
