Successive inactivation of the force-generating units of sodium-driven bacterial flagellar motors by a photoreactive amiloride analog.
Like amiloride, 6-iodoamiloride (6-IA) competitively and reversibly inhibits rotation of the Na(+)-driven flagellar motors of alkalophilic Bacillus cells. However, when 6-IA-treated cells are irradiated with UV light, motility is irreversibly inhibited. This treatment does not alter the membrane potential or affect Na(+)-coupled alpha-aminoisobutyrate transport. An increase in the Na+ concentration during UV irradiation substantially protects the motors from irreversible inhibition. Thus, photoactivated 6-IA seems to bind specifically and covalently at or around the Na(+)-interaction site of the force-generating units of the motors to inhibit motor rotation irreversibly. Rotation of each motor, which is monitored using tethered alkalophilic Bacillus cells, is also inhibited by photoactivated 6-IA. In this case, however, the rotation rate during UV irradiation decreases stepwise, suggesting the presence of several independently functioning force-generating units in a motor. From the data of 14 tethered cells, the number of units/motor is estimated to be 5-9.
Muramoto
K
K
Department of Molecular Biology, Faculty of Science, Nagoya University, Japan.
Sugiyama
S
S
Cragoe
E J
EJ
Imae
Y
Y
D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D001407:Bacillus / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D005407:Flagella / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D007700:Kinetics; D012964:Sodium / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors; D014466:Ultraviolet Rays
D012965:Sodium Chloride; C029230:6-iodoamiloride; D000584:Amiloride; D012964:Sodium