Niki H, Imamura R, Kitaoka M, Yamanaka K, Ogura T, Hiraga S
Department of Molecular Cell Biology, Kumamoto University School of Medicine, Japan.
EMBO J. 1992 Dec;11(13):5101-9. doi: 10.1002/j.1460-2075.1992.tb05617.x.
mukB mutants of Escherichia coli are defective in the correct partitioning of replicated chromosomes. This results in the appearance of normal-sized anucleate (chromosome-less) cells during cell proliferation. Based on the nucleotide sequence of the mukB gene, the MukB protein of 177 kDa was predicted to be a filamentous protein with globular domains at the ends, and also having DNA binding and nucleotide binding abilities. Here we present evidence that the purified MukB protein possesses these characteristics. MukB forms a homodimer with a rod-and-hinge structure having a pair of large, C-terminal globular domains at one end and a pair of small, N-terminal globular domains at the opposite end; it tends to bend at a middle hinge site of the rod section. Chromatography in a DNA-cellulose column and the gel retardation assay revealed that MukB possesses DNA binding activity. Photoaffinity cross-linking experiments showed that MukB binds to ATP and GTP in the presence of Zn2+. Throughout the purification steps, acyl carrier protein was co-purified with MukB.
大肠杆菌的mukB突变体在复制染色体的正确分配方面存在缺陷。这导致在细胞增殖过程中出现正常大小的无核（无染色体）细胞。根据mukB基因的核苷酸序列，预测177 kDa的MukB蛋白是一种丝状蛋白，两端具有球状结构域，并且还具有DNA结合和核苷酸结合能力。在此，我们提供证据表明纯化的MukB蛋白具有这些特征。MukB形成一种具有杆状和铰链结构的同型二聚体，一端有一对大的C末端球状结构域，另一端有一对小的N末端球状结构域；它倾向于在杆状部分的中间铰链位点处弯曲。在DNA - 纤维素柱上进行的色谱分析和凝胶阻滞试验表明MukB具有DNA结合活性。光亲和交联实验表明，在Zn2 +存在下，MukB与ATP和GTP结合。在整个纯化步骤中，酰基载体蛋白与MukB共纯化。
