STUDIES OF FUNCTIONS INVOLVED IN GENETIC RECOMBINATION

F-质粒蛋白CcdB可杀死大肠杆菌细胞 表达它，除非他们也表达它的抑制物CCDA。Ccdb的作用方式 抑制DNA旋转酶，使其切割染色体DNA。 我们研究了CcdB与DNA旋转酶的相互作用。我们 发现CcdB蛋白之间存在两种不同的复合体 和旋转酶。一种复合体(可能是致命的)会导致旋转酶 切断DNA，但不能明显抑制超螺旋。这个 其他复合体可以抑制超螺旋，但不能切割DNA。这 第二个复合体可以从细胞中分离出来，但它在体外形成 需要CcdB和gyrA蛋白变性，然后 在一起重修旧好。这两个复合体似乎涉及相同的 CcdB和Gyra上的官能团。这些结果现在正在被 与GyrA和CcdB蛋白的结晶学数据比较 它们正在变得可用。

The F-plasmid protein CcdB kills E. coli cells that express it, unless they also express its inhibitor CcdA. CcdB acts by inhibiting DNA gyrase and causing it to cleave chromosomal DNA. We have studied the interaction of CcdB with DNA gyrase. We found that there are two different complexes between CcdB protein and gyrase. One complex (probably the lethal one) causes gyrase to cleave DNA, but does not appreciably inhibit supercoiling. The other complex inhibits supercoiling but does not cleave DNA. This second complex can be isolated from cells, but its formation in vitro requires the CcdB and GyrA proteins to be denatured and then renatured together. Both complexes appear to involve the same functional groups on CcdB and GyrA. These results are now being compared to crystallographic data on the GyrA and CcdB proteins that are becoming available.