Identification of flagellar hook and basal body gene products (FlaFV, FlaFVI, FlaFVII and FlaFVIII) in Salmonella typhimurium
Identification of flagellar hook and basal body gene products (FlaFV, FlaFVI, FlaFVII and FlaFVIII) in Salmonella typhimurium
复制标题
鼠伤寒沙门氏菌鞭毛钩和基体基因产物（FlaFV、FlaFVI、FlaFVII 和 FlaFVIII）的鉴定
作者：
M. Homma;K. Ohnishi;T. Iino;R. Macnab
克隆了鼠伤寒沙门氏菌的鞭毛基因flaFV、flaFVII和flaFVIII，并通过同源基因缺陷的大肠杆菌突变体的互补来验证它们在给定质粒上的存在。通过在小细胞系统中放射性标记将基因产物鉴定为具有以下分子量的蛋白质：FlaFV，42千道尔顿（kDa）; FlaFVI，32 kDa; FlaFVII，30 kDa;和FlaFVIII，27 kDa。这些数据，再加上等电聚焦数据，确认基因产物分配鞭毛组件间接从突变体的研究。鞭毛组分通过信号肽依赖性或鞭毛特异性途径转运。与其在基体的外膜环中的位置一致，蛋白FlaFVIII似乎使用信号肽依赖性途径，因为它以前体形式合成并加工（推测通过肽裂解）成成熟形式;通过添加质子离子载体抑制成熟过程。小细胞中合成的蛋白质定位如下：FlaFVIII定位于可溶性部分（细胞质）;前FlaFVIII和FlaFVIII定位于颗粒部分（膜或高分子量聚集体）; FlaFV和FlaFVII定位于两种部分。这些位置在已知的或怀疑的作用在鞭毛器的意义进行了讨论。
The flagellar genes flaFV, flaFVII, and flaFVIII of Salmonella typhimurium were cloned, and their presence on a given plasmid was verified by complementation of Escherichia coli mutants defective in the homologous genes. The gene products were identified by radiolabeling in a minicell system as being proteins of the following molecular masses: FlaFV, 42 kilodaltons (kDa); FlaFVI, 32 kDa; FlaFVII, 30 kDA; and FlaFVIII, 27 kDa. These data, together with isoelectric focusing data, confirm gene product assignments of flagellar components made indirectly from mutant studies. Flagellar components are transported by either a signal peptide-dependent or a flagellar-specific pathway. Consistent with its location in the outer membrane ring of the basal body, protein FlaFVIII seems to use the signal peptide-dependent pathway, since it was synthesized in a precursor form and processed, presumably by peptide cleavage, to a mature form; the maturation process was inhibited by addition of a proton ionophore. Proteins synthesized in minicells were localized as follows: FlaFVI was localized to the soluble fraction (cytoplasm); pre-FlaFVIII and FlaFVIII were localized to the particulate fraction (membrane or high-molecular-weight aggregate); FlaFV and FlaFVII were localized to both fractions. The significance of these locations in terms of known or suspected roles in the flagellar apparatus is discussed.