McCarter L L
Immunology Department IMM17-A, Scripps Research Institute, La Jolla, California 92037.
J Bacteriol. 1994 Jul;176(14):4219-25. doi: 10.1128/jb.176.14.4219-4225.1994.
Energy to power the rotation of bacterial flagella can be derived from the proton or sodium transmembrane potential. Until now, genes encoding a bacterial sodium-type flagellar motor have not been defined. A gene, motY, encoding one component of the sodium-type flagellar motor of Vibrio parahaemolyticus was cloned by complementation of a Mot- mutant strain. Sequencing revealed an open reading frame of 879 nucleotides in which a transposon conferring a motility defect mapped. Overexpression of motY in Escherichia coli allowed identification of a product 33 kDa in apparent size on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This size correlated well with the predicted molecular mass of 33,385 Da. Unlike mot genes identified in other bacteria, localized transposon mutagenesis suggested that the locus was not an extended region containing multiple genes required for swimming motility. Sequencing upstream and downstream of motY confirmed that the gene maps alone and placed it within a locus homologous to the E. coli rnt locus. Although data bank searches failed to reveal significant similarity to known motility components, the carboxyl terminus of MotY showed extensive homology to a number of outer membrane proteins known to interact with peptidoglycan, including OmpA and peptidoglycan-associated lipoproteins. To a limited extent, this domain could also be identified in the Bacillus subtilis MotB protein. This finding suggests that MotY plays the role of a stator in the sodium flagellar motor, stabilizing the force-generating unit through direct interaction with the cell wall.
为细菌鞭毛旋转提供动力的能量可来自质子或钠离子跨膜电位。到目前为止，编码细菌钠型鞭毛马达的基因尚未明确。通过对Mot-突变菌株进行互补，克隆了编码副溶血性弧菌钠型鞭毛马达一个组分的基因motY。测序显示一个879个核苷酸的开放阅读框，其中一个导致运动缺陷的转座子定位于此。在大肠杆菌中过表达motY，使得能够在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳上鉴定出一个表观大小为33 kDa的产物。这个大小与预测的33385 Da分子量非常吻合。与在其他细菌中鉴定出的mot基因不同，局部转座子诱变表明该基因座不是一个包含游泳运动所需多个基因的扩展区域。对motY上下游进行测序证实该基因单独定位，并将其置于与大肠杆菌rnt基因座同源的一个基因座内。尽管数据库搜索未能揭示与已知运动组分有显著相似性，但MotY的羧基末端与许多已知与肽聚糖相互作用的外膜蛋白显示出广泛的同源性，包括OmpA和肽聚糖相关脂蛋白。在一定程度上，这个结构域在枯草芽孢杆菌MotB蛋白中也能被识别。这一发现表明MotY在钠型鞭毛马达中起定子的作用，通过与细胞壁直接相互作用稳定产生力的单元。
