Bryan R, Purucker M, Gomes S L, Alexander W, Shapiro L
Proc Natl Acad Sci U S A. 1984 Mar;81(5):1341-5. doi: 10.1073/pnas.81.5.1341.
The biosynthesis of the single polar flagellum and the proteins that comprise the chemotaxis methylation machinery are both temporally and spacially regulated during the Caulobacter crescentus cell-division cycle. The genes involved in these processes are widely separated on the chromosome. The region of the chromosome defined by flaE mutations contains at least one flagellin structural gene and appears to regulate flagellin synthesis and flagellar assembly. The protein product of the adjacent flaY gene was found to be required to regulate the expression of several flagellin proteins and the assembly of a functional flagellum. We demonstrate here that each of these genes is also required for the expression of chemotaxis methylation genes known to map elsewhere on the chromosome. In order to study the regulation of these genes, plasmids were constructed that contain either an intact flaYE region or deletions in the region of flaY. These plasmids were mated into a wild-type strain and into strains containing various Tn5 insertion and deletion mutations and a temperature-sensitive mutation in the flaYE region. The presence of a plasmid containing the flaYE region allowed the mutant strains to swim and to exhibit chemotaxis, to synthesize increased amounts of the flagellins, to methylate their "methyl-accepting chemotaxis proteins" (MCPs), and to regain wild-type levels of methyltransferase activity. Chromosomal deletions that extend beyond the cloned region were not complemented by this plasmid. Plasmids containing small deletions in the flaY region failed to restore to any flaY or flaE mutants the ability to swim or to assemble a flagellar filament. When mated into a wild-type strain, plasmids bearing deletions in the flaY region were found to be recessive. The pleiotropic regulation of flagellin synthesis, assembly, and chemotaxis methylation functions exhibited by both the flaY and flaE genes suggest that their gene products function in a regulatory hierarchy that controls both flagellar and chemotaxis gene expression.
在新月柄杆菌细胞分裂周期中，单极鞭毛的生物合成以及构成趋化作用甲基化机制的蛋白质在时间和空间上均受到调控。参与这些过程的基因在染色体上广泛分布。由flaE突变定义的染色体区域至少包含一个鞭毛蛋白结构基因，并且似乎调控鞭毛蛋白的合成和鞭毛组装。发现相邻的flaY基因的蛋白质产物是调控几种鞭毛蛋白的表达以及功能性鞭毛组装所必需的。我们在此证明，这些基因中的每一个对于已知定位于染色体其他位置的趋化作用甲基化基因的表达也是必需的。为了研究这些基因的调控，构建了含有完整flaYE区域或flaY区域缺失的质粒。将这些质粒与野生型菌株以及含有各种Tn5插入和缺失突变以及flaYE区域温度敏感突变的菌株进行接合。含有flaYE区域的质粒的存在使突变菌株能够游动并表现出趋化性，能够合成更多量的鞭毛蛋白，使其“甲基接受趋化蛋白”（MCP）甲基化，并恢复野生型水平的甲基转移酶活性。延伸至克隆区域之外的染色体缺失不能被该质粒互补。含有flaY区域小缺失的质粒无法恢复任何flaY或flaE突变体的游动能力或组装鞭毛丝的能力。当与野生型菌株接合时，发现携带flaY区域缺失的质粒是隐性的。flaY和flaE基因所表现出的对鞭毛蛋白合成、组装和趋化作用甲基化功能的多效性调控表明，它们的基因产物在控制鞭毛和趋化作用基因表达的调控层级中发挥作用。
