Yamanaka K, Ogura T, Niki H, Hiraga S
Department of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University School of Medicine, Japan.
Mol Gen Genet. 1996 Feb 25;250(3):241-51. doi: 10.1007/BF02174381.
We have previously reported that the MukB protein is essential for chromosome partitioning in Escherichia coli and that mukB mutants produce anucleate cells and are temperature-sensitive for colony formation. The mukB gene maps at 21 min on the E. coli chromosome and smtA-mukF-mukE-mukB genes might comprise an operon, which is transcribed in a clockwise direction. Here, we report that mukF and mukE null mutants are both temperature-sensitive for colony formation and produce anucleate cells even at the permissive temperature. These phenotypes are the same as those observed in the mukB null mutant. The primary sequence of MukF includes a leucine zipper structure and an acidic domain. Mutational analysis revealed that both are required for MukF function. When the MukF protein was overproduced in the wild-type strain, anucleate cells were produced. In contrast, overproduction of either MukE or MukB did not cause the defect. In null mutants for the mukF, mukE, and mukB genes, the synchronous initiation of chromosome replication was not affected. The mini-F plasmid was as stably maintained in these mutants as in the wild-type strain. These results indicate that the MukF, MukE, and MukB proteins are involved in the chromosome partitioning steps, but are not required for mini-F plasmid partitioning.
我们之前报道过，MukB蛋白对大肠杆菌中的染色体分离至关重要，并且mukB突变体产生无核细胞，且在菌落形成方面对温度敏感。mukB基因定位于大肠杆菌染色体的21分钟处，smtA-mukF-mukE-mukB基因可能组成一个操纵子，该操纵子按顺时针方向转录。在此，我们报道mukF和mukE缺失突变体在菌落形成方面均对温度敏感，甚至在允许温度下也会产生无核细胞。这些表型与在mukB缺失突变体中观察到的相同。MukF的一级序列包含一个亮氨酸拉链结构和一个酸性结构域。突变分析表明两者都是MukF功能所必需的。当MukF蛋白在野生型菌株中过量表达时，会产生无核细胞。相比之下，MukE或MukB的过量表达不会导致这种缺陷。在mukF、mukE和mukB基因的缺失突变体中，染色体复制的同步起始不受影响。mini-F质粒在这些突变体中与在野生型菌株中一样稳定维持。这些结果表明，MukF、MukE和MukB蛋白参与染色体分离步骤，但mini-F质粒分离不需要它们。
