Feng J, Yamanaka K, Niki H, Ogura T, Hiraga S
Department of Molecular Cell Biology, Kumamoto University School of Medicine, Japan.
Mol Gen Genet. 1994 Apr;243(2):136-47. doi: 10.1007/BF00280310.
The nucleotide sequence was determined of the region upstream of the mukB gene of Escherichia coli. Two new genes were found, designated kicA and kicB (killing of cell); the gene order is kicB-kicA-mukB. Promoter activities were detected in the regions immediately upstream of kicB and kicA, but not in front of mukB. Gene disruption experiments revealed that the kicA disruptant was nonviable, but the kicB-disrupted mutant and the mutant lacking both the kicB and kicA genes were able to grow. When kicA disruptant cells bearing a temperature-sensitive replication plasmid carrying the kicA+ gene were grown at 30 degrees C and then transferred to 42 degrees C, the mutant cells gradually lost colony-forming ability, even in the presence of a mukB+ plasmid. Rates of protein synthesis, but not of RNA or DNA synthesis, fell dramatically during incubation at 42 degrees C. These results suggested that the kicB gene encodes a killing factor and the kicA gene codes for a protein that suppresses the killing function of the kicB gene product. It was also demonstrated that KicA and KicB can function as a post-segregational killing system, when the genes are transferred from the E. coli chromosome onto a plasmid.
测定了大肠杆菌mukB基因上游区域的核苷酸序列。发现了两个新基因，命名为kicA和kicB（细胞杀伤）；基因顺序为kicB - kicA - mukB。在kicB和kicA紧上游区域检测到启动子活性，但在mukB前方未检测到。基因破坏实验表明，kicA破坏株无法存活，但kicB破坏突变体以及缺失kicB和kicA基因的突变体能够生长。当携带携带kicA⁺基因的温度敏感复制质粒的kicA破坏株细胞在30℃生长然后转移至42℃时，即使存在mukB⁺质粒，突变细胞的集落形成能力也逐渐丧失。在42℃孵育期间，蛋白质合成速率大幅下降，但RNA或DNA合成速率未下降。这些结果表明，kicB基因编码一种杀伤因子，而kicA基因编码一种抑制kicB基因产物杀伤功能的蛋白质。还证明，当这些基因从大肠杆菌染色体转移到质粒上时，KicA和KicB可作为一种后分离杀伤系统发挥作用。
