Atsumi T, Sugiyama S, Cragoe E J, Imae Y
Department of Molecular Biology, Faculty of Science, Nagoya University, Japan.
J Bacteriol. 1990 Mar;172(3):1634-9. doi: 10.1128/jb.172.3.1634-1639.1990.
Amiloride, a specific inhibitor for the Na(+)-driven flagellar motors of alkalophilic Bacillus strains, was found to cause growth inhibition; therefore, the use of amiloride for the isolation of motility mutants was difficult. On the other hand, phenamil, an amiloride analog, inhibited motor rotation without affecting cell growth. A concentration of 50 microM phenamil completely inhibited the motility of strain RA-1 but showed no effect on the membrane potential, the intracellular pH, or Na(+)-coupled amino acid transport, which was consistent with the fact that there was no effect on cell growth. Kinetic analysis of the inhibition of motility by phenamil indicated that the inhibition was noncompetitive with Na+ in the medium. A motility mutant was isolated as a swarmer on a swarm agar plate containing 50 microM phenamil. The motility of the mutant showed an increased resistance to phenamil but normal sensitivity to amiloride. These results suggest that phenamil and amiloride interact at different sites on the motor. By examining various bacterial species, phenamil was found to be a specific and potent inhibitor for the Na(+)-driven flaggellar motors not only in various strains of alkalophilic Bacillus spp. but also in a marine Vibrio sp.
氨氯吡脒是嗜碱芽孢杆菌菌株中由钠离子驱动的鞭毛马达的特异性抑制剂，发现它会导致生长抑制；因此，利用氨氯吡脒来分离运动突变体很困难。另一方面，氨氯吡脒类似物非那明抑制马达旋转但不影响细胞生长。50微摩尔浓度的非那明完全抑制了RA-1菌株的运动性，但对膜电位、细胞内pH值或与钠离子偶联的氨基酸转运没有影响，这与对细胞生长无影响的事实是一致的。对非那明抑制运动性的动力学分析表明，这种抑制在培养基中对钠离子是非竞争性的。在含有50微摩尔非那明的群体琼脂平板上，作为群体游动菌分离出了一个运动突变体。该突变体的运动性对非那明表现出增强的抗性，但对氨氯吡脒具有正常的敏感性。这些结果表明，非那明和氨氯吡脒在马达上的不同位点相互作用。通过检测各种细菌物种，发现非那明不仅是嗜碱芽孢杆菌属各种菌株中由钠离子驱动的鞭毛马达的特异性强效抑制剂，也是海洋弧菌属中该马达的特异性强效抑制剂。
