Intracellular Na+ kinetically interferes with the rotation of the Na(+)-driven flagellar motors of Vibrio alginolyticus.
To understand the mechanism of Na+ movement through the force-generating units of the Na(+)-driven flagellar motors of Vibrio alginolyticus, the effect of intracellular Na+ concentration on motor rotation was investigated. Control cells containing about 50 mM Na+ showed good motility even at 10 mM Na+ in the medium, i.e. in the absence of an inwardly directed Na+ gradient. In contrast, Na(+)-loaded cells containing about 400 mM Na+ showed very poor motility at 500 mM Na+ in the medium, i.e. even in the presence of an inwardly directed Na+ gradient. The membrane potential of the cells, which is a major driving force for the motor under these conditions, was not detectably altered, and consistently with this, Na(+)-coupled sucrose transport was only partly reduced in the Na(+)-loaded cells. Motility of the Na(+)-loaded cells was restored by decreasing the intracellular Na+ concentration, and the rate of restoration of motility correlated with the rate of the Na+ decrease. These results indicate that the absolute concentration of the intracellular Na+ is a determinant of the rotation rate of the Na(+)-driven flagellar motors of V. alginolyticus. A simple explanation for this phenomenon is that the force-generating unit of the motor has an intracellular Na(+)-binding site, at which the intracellular Na+ kinetically interferes with the rate of Na+ influx for motor rotation.
Yoshida
S
S
Department of Molecular Biology, Faculty of Science, Nagoya University, Japan.
Sugiyama
S
S
Hojo
Y
Y
Tokuda
H
H
Imae
Y
Y
D000621:Aminoisobutyric Acids / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002586:Cesium / Q000494:pharmacology; D002794:Choline / Q000494:pharmacology; D005407:Flagella / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D008954:Models, Biological; D009068:Movement; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000502:physiology*; D013395:Sucrose / Q000378:metabolism; D014733:Vibrio / Q000187:drug effects / Q000502:physiology*
D000621:Aminoisobutyric Acids; C100049:2-aminoisobutyric acid; D002586:Cesium; D013395:Sucrose; D012964:Sodium; D002794:Choline; D011188:Potassium