LOCALIZATION OF THE SALMONELLA-TYPHIMURIUM FLAGELLAR SWITCH PROTEIN FLIG TO THE CYTOPLASMIC M-RING FACE OF THE BASAL BODY
LOCALIZATION OF THE SALMONELLA-TYPHIMURIUM FLAGELLAR SWITCH PROTEIN FLIG TO THE CYTOPLASMIC M-RING FACE OF THE BASAL BODY
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DOI：
10.1073/pnas.89.14.6304
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发表时间：
1992-07-15
影响因子：
11.1
通讯作者：
MACNAB, RM
中科院分区：
文献类型：
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作者：
FRANCIS, NR;IRIKURA, VM;MACNAB, RM
细菌鞭毛的旋转方向由鞭毛开关决定。我们已将鼠伤寒沙门氏菌的开关蛋白之一FliG定位在鞭毛基体的M环的细胞质面。这一定位是通过发现两个自发突变体得以实现的，在这两个突变体中，fliF（M环）和fliG（开关）基因发生了框内融合。在第一个突变体中，fliF的3'端缺失7个碱基对，产生了一个基本全长的融合蛋白。在第二个突变体中，一个更大的缺失导致产生一种融合蛋白，其中FliF的羧基末端的56个氨基酸和FliG的氨基末端的94个氨基酸缺失。这两种菌株都能运动且能进行转换；第一种菌株有顺时针偏向，第二种菌株有逆时针偏向。对分离的钩 - 基体复合物进行凝胶电泳和免疫印迹分析，证实它们含有融合蛋白。电子显微镜观察显示M环的细胞质面有额外的物质，这些物质可被抗FliG抗体标记。我们得出结论，FliG的天然位置在M环的细胞质面，并且野生型细胞中FliF和FliG之间的化学计量比可能是1∶1。
The direction of rotation of the bacterial flagellum is determined by the flagellar switch. We have localized FliG, one of the switch proteins of Salmonella typhimurium, to the cytoplasmic face of the M ring of the flagellar basal body. This localization was made possible by the discovery of two spontaneous mutants in which the fliF (M ring) and fliG (switch) genes were fused in-frame. In the first mutant, a deletion of 7 base pairs at the 3' end of fliF resulted in an essentially full-length fusion protein. In the second mutant, a larger deletion resulted in a fusion in which 56 amino acids from the carboxyl terminus of FliF and 94 amino acids from the amino terminus of FliG were lost. Both strains were motile and underwent switching; the first strain had a clockwise bias, and the second strain had a counterclockwise bias. Gel electrophoresis and immunoblotting of isolated hook-basal-body complexes verified that they contained the fusion proteins. Electron microscopy revealed additional mass at the cytoplasmic face of the M ring, which could be decorated with anti-FliG antibody. We conclude that the natural location for FliG is at the cytoplasmic face of the M ring and that the stoichiometric ratio between FliF and FliG in wild-type cells is probably 1:1.