A novel mechanism of cation/substrate cotransport: Na+/H+/adenosine cotransport in Vibrio parahaemolyticus.
Adenosine is actively transported with Na+ in Vibrio parahaemolyticus (Sakai, Y., Tsuda, M., Tsuchiya, T. (1987) Biochim, Biophys. Acta 893, 43-48). The proton conductor carbonylcyanide m-chlorophenylhydrazone, CCCP, strongly inhibited active transport of adenosine at pH 8.5 as well as at pH 7.0. This seemed peculiar because the driving force, an electrochemical potential of Na+, is established by the Na(+)-extruding respiratory chain at pH 8.5 in this organism, although it is established by the function of the Na+/H+ antiporter at pH 7.0. This suggested that H+ might be involved in the adenosine transport. We detected H+ uptake induced by adenosine influx in V. parahaemolyticus cells in the presence of Na+, but not in its absence, suggesting the occurrence of Na+/H+/adenosine cotransport. We isolated formycin A-resistant mutants which showed defective adenosine transport. The mutation resulted in simultaneous losses of Na+ uptake and H+ uptake induced by adenosine. In revertants from these mutants the Na+ uptake and H+ uptake were restored simultaneously. The frequencies of reversion were in the order of 10(-7), indicating that the mutations were single mutations; namely that Na+/adenosine cotransport and H+/adenosine cotransport took place via the same carrier. Thus, we conclude that adenosine is transported by the novel mechanism of Na+/H+/adenosine cotransport in V. parahaemolyticus.
Okabe
Y
Y
Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Sakai-Tomita
Y
Y
Mitani
Y
Y
Tsuda
M
M
Tsuchiya
T
T
D000241:Adenosine / Q000378:metabolism*; D001693:Biological Transport, Active; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006859:Hydrogen / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation; D012964:Sodium / Q000378:metabolism*; D014736:Vibrio parahaemolyticus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006859:Hydrogen; D012964:Sodium; D000241:Adenosine