Ali J A, Lohman T M
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
Science. 1997 Jan 17;275(5298):377-80. doi: 10.1126/science.275.5298.377.
The kinetic mechanism by which the DNA repair helicase UvrD of Escherichia coli unwinds duplex DNA was examined with the use of a series of oligodeoxynucleotides with duplex regions ranging from 10 to 40 base pairs. Single-turnover unwinding experiments showed distinct lag phases that increased with duplex length because partially unwound DNA intermediate states are highly populated during unwinding. Analysis of these kinetics indicates that UvrD unwinds duplex DNA in discrete steps, with an average "step size" of 4 to 5 base pairs (approximately one-half turn of the DNA helix). This suggests an unwinding mechanism in which alternating subunits of the dimeric helicase interact directly with duplex DNA.
利用一系列双链区域长度从10到40个碱基对的寡脱氧核苷酸，研究了大肠杆菌DNA修复解旋酶UvrD解开双链DNA的动力学机制。单轮解旋实验显示出明显的滞后阶段，该阶段随双链长度增加，因为在解旋过程中部分解旋的DNA中间状态大量存在。对这些动力学的分析表明，UvrD以离散步骤解开双链DNA，平均“步长”为4至5个碱基对（约为DNA螺旋的半圈）。这表明了一种解旋机制，即二聚体解旋酶的交替亚基直接与双链DNA相互作用。
