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DNA复制和细胞分裂的控制回路的遗传背景。两个质粒编码基因letA和letD控制F质粒DNA复制与宿主细菌细胞分裂之间的耦合（Miki, et al., j.l l. biol .）。174 605-625 (1984)；Miki等，同上，174 627-646(1984))。letD基因产物抑制细菌的细胞分裂，letA基因产物抑制letD基因产物的抑制活性，诱导细胞分裂。为了研究参与这种偶联的细菌基因，我们试图确定F质粒分裂抑制剂的靶标。在携带FletA突变体的宿主中，可以逃脱letD产物生长抑制的细菌突变体中获得letD基因产物的假定靶蛋白突变体。通过噬菌体Pl介导的转导、互补分析和核苷酸测序，将分离的突变体（TDI）分为5组：携带groES突变的突变体（Miki, et al., j.l l. biol .）；201327 -338 (1988)), groEL, gyrA， tdiC或tdiD基因。gyrA基因编码DNA gyrase的亚基a，这种酶负责在一轮复制后断开环形子染色体的连接，并维持细菌染色体的超螺旋密度。在高拷贝质粒上克隆的野生型gyrA基因抑制了letD基因产物引起的生长抑制，表明过量生产gyrA基因产物克服了letD基因产物的抑制活性。据推测，letD基因产物直接作用于dna旋切酶，从而抑制宿主细菌的染色体分离和细胞分裂。据推测，groES和groEL基因产物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。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