Amiloride, a specific inhibitor for the Na+-driven flagellar motors of alkalophilic Bacillus

Na+-driven flagellar motors of alkalophilic Bacillus were found to be inhibited by amiloride, a potent inhibitor for many Na+-coupled systems. A concentration of 0.5 mM of amiloride completely inhibited motility but showed almost no effect on the membrane potential, the intracellular pH homeostasis,...

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Bibliographic Details
Published in:The Journal of biological chemistry 1988-06, Vol.263 (17), p.8215-8219
Main Authors: Sugiyama, S, Cragoe, E J, Imae, Y
Format: Article
Language:English
Subjects:
Amiloride - pharmacology
Bacillus - drug effects
Bacteriology
Biological and medical sciences
Flagella - drug effects
Fundamental and applied biological sciences. Psychology
Hydrogen-Ion Concentration
Kinetics
Membrane Potentials - drug effects
Microbiology
Motility, taxis
Osmolar Concentration
Sodium - metabolism
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Summary:Na+-driven flagellar motors of alkalophilic Bacillus were found to be inhibited by amiloride, a potent inhibitor for many Na+-coupled systems. A concentration of 0.5 mM of amiloride completely inhibited motility but showed almost no effect on the membrane potential, the intracellular pH homeostasis, and the ATP content of the cells. Furthermore, the activity of a Na+-coupled amino acid transport system was reduced only by half by this concentration of amiloride. Thus, the inhibition of motility of alkalophilic Bacillus by amiloride was rather specific. The inhibition of motility produced by amiloride was restored by increasing Na+ concentrations in the medium. Kinetic analysis of the data revealed that the inhibition was competitive with respect to the concentration of Na+ in the medium. Therefore, it is quite logical to assume that amiloride inhibits the rotation of the Na+-driven flagellar motors of alkalophilic Bacillus by competing with Na+ at the force-generating site of the motor. Some amiloride analogs known to selectively inhibit Na+ channels were potent inhibitors for the flagellar motors, suggesting that the Na+-interacting site of the motors has some similarity to that of the Na+ channels.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)68465-0