Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, USA.
Science. 2011 Sep 23;333(6050):1746-9. doi: 10.1126/science.1206023.
Nonhexameric helicases use adenosine triphosphate (ATP) to unzip base pairs in double-stranded nucleic acids (dsNAs). Studies have suggested that these helicases unzip dsNAs in single-base pair increments, consuming one ATP molecule per base pair, but direct evidence for this mechanism is lacking. We used optical tweezers to follow the unwinding of double-stranded RNA by the hepatitis C virus NS3 helicase. Single-base pair steps by NS3 were observed, along with nascent nucleotide release that was asynchronous with base pair opening. Asynchronous release of nascent nucleotides rationalizes various observations of its dsNA unwinding and may be used to coordinate the translocation speed of NS3 along the RNA during viral replication.
非六聚体解旋酶利用三磷酸腺苷（ATP）将双链核酸（dsNAs）中的碱基对解开。研究表明，这些解旋酶以单碱基对的增量解开 dsNAs，每解开一个碱基对消耗一个 ATP 分子，但这种机制的直接证据尚缺乏。我们使用光学镊子跟踪丙型肝炎病毒 NS3 解旋酶解开双链 RNA 的过程。观察到 NS3 以单碱基对的步幅移动，同时伴随着与碱基对打开不同步的新生核苷酸释放。新生核苷酸的异步释放解释了其 dsNA 解旋的各种观察结果，并且可能用于协调病毒复制过程中 NS3 沿 RNA 的易位速度。
