Churchill J J, Kowalczykowski S C
Section of Microbiology, Graduate Group in Biochemistry, University of California, Davis, CA, 95616, USA.
J Mol Biol. 2000 Mar 31;297(3):537-42. doi: 10.1006/jmbi.2000.3590.
Genetic recombination in Escherichia coli is stimulated by the recombination hotspot Chi (chi), a regulatory element that modifies the activities of the RecBCD enzyme and leads to loading of the DNA strand exchange protein, RecA, onto the chi-containing DNA strand. The RecBC enzyme, which lacks the RecD subunit, loads RecA protein constitutively, in a manner that is independent of chi. Using a truncated RecBC enzyme lacking the 30 kDa C-terminal domain of the RecB subunit, we show that this domain is necessary for RecA protein-loading. We propose that this domain harbors a site that interacts with RecA protein, recruiting it to single-stranded DNA during unwinding. This ability of a translocating enzyme to deliver material (RecA protein) to a specific target site (the chi sequence) parallels that of other cellular motor proteins.
大肠杆菌中的基因重组受到重组热点Chi（chi）的刺激，Chi是一种调控元件，可改变RecBCD酶的活性，并导致DNA链交换蛋白RecA加载到含chi的DNA链上。缺乏RecD亚基的RecBC酶以与chi无关的方式持续加载RecA蛋白。使用一种缺失RecB亚基30 kDa C末端结构域的截短型RecBC酶，我们发现该结构域对于RecA蛋白的加载是必需的。我们提出，该结构域含有一个与RecA蛋白相互作用的位点，在解旋过程中将其招募到单链DNA上。这种易位酶将物质（RecA蛋白）递送至特定靶位点（chi序列）的能力与其他细胞运动蛋白类似。
