Graduate School of Natural Science and Technology, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
Mol Genet Genomics. 2011 Feb;285(2):163-74. doi: 10.1007/s00438-010-0594-8. Epub 2010 Dec 17.
The motor proteins around the flagellar basal body consist of two cytoplasmic membrane proteins, MotA and MotB, and function as a complex that acts as the stator to generate the torque that drives rotation. Genome analysis of several Pseudomonas syringae pathovars revealed that there are two sets of genes encoding motor proteins: motAB and motCD. Deduced amino acid sequences for MotA/B and MotC/D showed homologies to the H(+)-driven stator from Escherichia coli and Na(+)-driven stator from Vibrio alginolyticus, respectively. However, the swimming motility of P. syringae pv. tabaci (Pta) 6605 was inhibited by the protonophore carbonyl cyanide m-chlorophenylhydrazone but not by the sodium stator-specific inhibitor phenamil. To identify a gene encoding the stator protein required for motility, ∆motAB, ∆motCD, and ∆motABCD mutants were generated. The ∆motCD mutant had remarkably reduced and the ∆motABCD mutant completely abolished swimming motilities, whereas the ∆motAB mutant retained some degree of these abilities. The ∆motCD and ∆motABCD mutants did not produce N-acyl-homoserine lactones (AHLs), quorum-sensing molecules in this pathogen, and remarkably reduced the ability to cause disease in host tobacco leaves, as we previously observed in the ∆fliC mutant strain. These results strongly indicate that both stator pairs in Pta 6605 are proton-dependent and that MotCD is important for not only flagellar motility but also for production of AHLs and the ability to cause disease in host plants.
鞭毛基体周围的马达蛋白由两个细胞质膜蛋白 MotA 和 MotB 组成，作为定子发挥作用，产生驱动旋转的扭矩。对几种丁香假单胞菌致病型的基因组分析表明，有两组编码马达蛋白的基因：motAB 和 motCD。推测的 MotA/B 和 MotC/D 氨基酸序列分别与大肠杆菌的 H(+)-驱动定子和弧菌 alginolyticus 的 Na(+)-驱动定子同源。然而，丁香假单胞菌 pv. tabaci (Pta) 6605 的游动性被质子载体羰基氰化物 m-氯苯腙抑制，但不受钠定子特异性抑制剂苯甲脒抑制。为了鉴定运动所需的定子蛋白编码基因，生成了 ∆motAB、∆motCD 和 ∆motABCD 突变体。∆motCD 突变体的泳动性显著降低，∆motABCD 突变体完全丧失泳动性，而 ∆motAB 突变体保留了一定程度的泳动性。∆motCD 和 ∆motABCD 突变体不产生 N-酰基高丝氨酸内酯 (AHLs)，这是该病原体中的群体感应分子，并且如我们之前在 ∆fliC 突变株中观察到的那样，显著降低了在宿主烟草叶片中引起疾病的能力。这些结果强烈表明，Pta 6605 中的两个定子对都是质子依赖性的，MotCD 不仅对鞭毛运动很重要，而且对 AHLs 的产生和在宿主植物中引起疾病的能力也很重要。
