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首页> 外文期刊>Journal of bacteriology >Intergenic Suppression between the Flagellar MS Ring Protein FliF of Salmonella and FlhA, a Membrane Component of Its Export Apparatus
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Intergenic Suppression between the Flagellar MS Ring Protein FliF of Salmonella and FlhA, a Membrane Component of Its Export Apparatus

机译：沙门氏菌鞭毛MS环蛋白FliF和FlhA，其出口设备的膜成分之间的基因间抑制。

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The MS ring of the flagellar basal body of Salmonellais an integral membrane structure consisting of about 26 subunits of a 61-kDa protein, FliF. Out of many nonflagellate fliFmutants tested, three gave rise to intergenic suppressors in flagellar region II. The pseudorevertants swarmed, though poorly; this partial recovery of motile function was shown to be due to partial recovery of export function and flagellar assembly. The three parental mutants were all found to carry the same mutation, a six-base deletion corresponding to loss of Ala-174 and Ser-175 in the predicted periplasmic domain of the FliF protein. The 19 intergenic suppressors identified all lay inflhA, and they consisted of 10 independent examples at the nucleotide level or 9 at the amino acid level. Since two of the nine corresponded to different substitutions at the same amino acid position, only eight positions in the FlhA protein have given rise to suppressors. Thus, FliF-FlhA intergenic suppression is a fairly rare event. FlhA is a component of the flagellar protein export apparatus, with an integral membrane domain encompassing the N-terminal half of the sequence and a cytoplasmic C-terminal domain. All of the suppressing mutations lay within the integral membrane domain. These mutations, when placed in a wild-type fliF background, had no mutant phenotype. In the fliF mutant background, mutant FlhA was dominant, yielding a pseudorevertant phenotype. Wild-type FlhA did not exert significant negative dominance in the pseudorevertant background, indicating that it does not compete effectively with mutant FlhA for interaction with mutant FliF. Mutant FliF was partially dominant over wild-type FliF in both the wild-type and second-site FlhA backgrounds. Membrane fractionation experiments indicated that thefliF mutation, though preventing export, was mild enough to permit assembly of the MS ring itself, and also assembly of the cytoplasmic C ring onto the MS ring. The data from this study provide genetic support for a model in which at least the FlhA component of the export apparatus physically interacts with the MS ring within which it is housed.
机译：沙门氏菌鞭毛基体的MS环是完整的膜结构，由61 kDa蛋白FliF的约26个亚基组成。在测试的许多非鞭毛 fliF 突变体中，有三个在鞭毛II区产生了基因间抑制子。伪复员蜂拥而至，尽管情况不佳。运动功能的部分恢复被证明是由于出口功能和鞭毛组装的部分恢复。发现三个亲本突变体均携带相同的突变，即六碱基缺失，对应于在FliF蛋白的预测周质结构域中Ala-174和Ser-175的缺失。 19种基因间抑制子均位于 flhA 中，由核苷酸水平的10个独立实例或氨基酸水平的9个组成。由于九个中的两个对应于相同氨基酸位置上的不同取代，因此FlhA蛋白中只有八个位置产生了抑制剂。因此，FliF-FlhA基因间抑制是相当罕见的事件。 FlhA是鞭毛蛋白输出设备的一个组成部分，具有完整的膜结构域，该结构域包含序列的N端一半和胞质C端结构域。所有抑制突变都位于完整的膜结构域内。这些突变置于野生型 fliF 背景中时，没有突变表型。在 fliF 突变体背景下，突变体FlhA占主导地位，产生了拟回复表型。野生型FlhA在假回复背景中没有发挥显着的负优势，表明它不能与突变FlhA有效竞争与突变FliF的相互作用。在野生型和第二位FlhA背景中，突变型FliF均部分优于野生型FliF。膜分离实验表明， fliF 突变虽然阻止了出口，但其轻度足以允许MS环本身组装，也可以将细胞质C环组装到MS环上。这项研究的数据为该模型提供了遗传支持，在该模型中，至少出口设备的FlhA成分与其所在的MS环发生了物理相互作用。

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