Moore K J, Lohman T M
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Biophys J. 1995 Apr;68(4 Suppl):180S-184S; discussion 184S-185S.
DNA helicases catalyze the unwinding of double-stranded (ds) DNA to yield the single-stranded (ss) DNA intermediates required in DNA replication, recombination, and repair. DNA helicases couple the free energy of nucleoside triphosphate (NTP) binding and hydrolysis to separate the two complementary DNA strands while also translocating vectorially along the DNA substrate. As such, helicases are functionally DNA motor proteins. The functional form of helicases generally appears to be oligomeric (usually dimers or hexamers), which provides the helicase with multiple DNA binding sites that are required for translocation and DNA unwinding. The affinity of ss- versus dsDNA for these multiple DNA binding sites is modulated allosterically by NTP binding, hydrolysis, and product release, which is central to helicase-catalyzed DNA unwinding. The mechanistic details of the DNA unwinding, translocation, and NTPase reactions are only starting to emerge. We discuss energy coupling by DNA helicases in general, and by the dimeric E. coli Rep helicase in particular, focusing on the similarities of these enzymes to classical motor proteins.
DNA解旋酶催化双链（ds）DNA解旋，产生DNA复制、重组和修复所需的单链（ss）DNA中间体。DNA解旋酶将核苷三磷酸（NTP）结合和水解的自由能耦合起来，以分离两条互补的DNA链，同时还沿DNA底物进行向量移位。因此，解旋酶在功能上是DNA运动蛋白。解旋酶的功能形式通常似乎是寡聚体（通常是二聚体或六聚体），这为解旋酶提供了移位和DNA解旋所需的多个DNA结合位点。单链与双链DNA对这些多个DNA结合位点的亲和力通过NTP结合、水解和产物释放而受到变构调节，这是解旋酶催化DNA解旋的核心。DNA解旋、移位和NTPase反应的机制细节才刚刚开始显现。我们总体讨论DNA解旋酶的能量耦合，特别是二聚体大肠杆菌Rep解旋酶的能量耦合，重点关注这些酶与经典运动蛋白的相似性。
