Genetic studies on the control of cell division in Escherichia coli. Cordination with DNA replication of the F plasmid.

利用F质粒研究了大肠杆菌中协调细胞DNA复制和细胞分裂的控制电路的遗传背景。两个质粒编码基因LetA和letD控制着F质粒的DNA复制和宿主细菌的细胞分裂之间的耦合(Miki等人，J.Mol.Biol.174 605-625(1984)；Miki等人，同上，174 627-646(1984))。LetD基因产物作用于抑制细菌的细胞分裂，而letA基因产物作用于抑制letD基因产物的抑制活性并诱导细胞分裂。为了研究参与这种偶联的杆菌基因，我们试图确定F质粒分裂抑制物的靶标。在逃脱letD产物生长抑制的细菌突变体中，获得了letD基因产物的推定靶蛋白的突变体，这种抑制发生在携带FletA突变体的宿主中。通过噬菌体Pl介导的转导、互补分析和核糖核酸…更多的去测序，将分离的突变体(TDI)分为五组：携带GROE突变的突变体(Miki等人，J.Mol.Biol)。201 327-338(1988))、GroEL、gyrA、tDIC或tdiD基因。GyrA基因编码DNA旋转酶的a亚基，这种酶负责在一轮复制后解除环状子体染色体的连接，并维持细菌染色体的超螺旋密度。克隆在高拷贝质粒上的野生型gyrA基因抑制了letD基因产物的生长抑制作用，说明gyrA基因产物的过量生产克服了letD基因产物的抑制活性。LetD基因产物可能直接作用于DNA旋转酶，结果是抑制了宿主细菌的染色体分离和细胞分裂。GroES和GroEL基因产物被认为作为分子伴侣参与了这些过程。TDIC和TdiD是新的基因，目前正在对它们的结构和功能进行分析。较少

The genetic background of the control circuit in Escherichia coli that co-ordinate DNA replication and cell division of the cells was studied using the F plasmid. Two plasmid coded genes letA and letD controls the coupling between DNA replication of the F plasmid and cell division of the host bacteria (Miki, et al., J.Mol.Biol. 174 605-625 (1984); Miki, et al., ibid., 174 627-646 (1984)). The letD gene product acts to inhibit cell division of the bacteria, whereas the letA gene product acts to suppress the inhibitory activity of the letD gene product and to induce cell division. To investigate bactrial genes that participate in this coupling, we attempted to identify the target of the division inhibitor of the F plasmid. Mutants of presumptive target proteins of the letD gene product were obtained among bacterial mutants that escaped the letD product growth inhibition that occurs in hosts carrying an FletA mutant. By phage Pl mediated transduction, complementation analysis and nucleoti … More de sequencing, the mutants isolated (TDI) were classified into five groups: mutants carrying mutations in the groES (Miki, et al., J.Mol.Biol. 201 327-338 (1988)), groEL, gyrA, tdiC or tdiD genes. The gyrA gene codes for subunit a of DNA gyrase, the enzyme responsible for unlinking circular daughter chromosome after a round of replication and for maintaining the superhelical density of the bacterial chromosome. Wild type gyrA gene cloned on a high copy plasmid suppressed the growth inhibition caused by the letD gene product, suggesting that overproduction of the gyrA gene product overcomes the inhibitory activity of the letD gene product. The letD gene product presumaly acts directly on dna gyrase and, as a result, inhibits segregation of the chromosome and cell division of the host bacteria. The groES and groEL gene products supposedly participate in these processes as molecular chaperones. The tdiC and tdiD are novel genes and analyses of their structure and function are now under way. Less