The mechanism of H
+ transport in
Rhodospirillum rubrum cells was investigated with respect to anion movement.
The cells of
R. rubrum showed a light-induced H
+ efflux, which required the intact cell membrane. The light-induced H
+ efflux was observed only in the presence of appropriate anions, such as Cl
- or N0
3-. The light-induced H
+ efflux was inhibited by inhibitors of cyclic electron transport, antimycin A and
o-phenanthroline, and uncouplers, carbonyl cyanide
m-chlorophenylhydrazone (CCCP) and 2, 4-dinitrophenol (DNP) at higher concentrations.
The light-induced H
+ efflux was stimulated by N-methylphenazonium methosulfate (PMS) and N, N, N', N'-tetramethyl-
p-phenylenediamine (TMPD). PMS and TMPD partially overcame the inhibition by antimycin A and
o-phenanthroline. The light-induced H
+ efflux was stimulated by CCCP or DNP at lower concentrations in the presence of Cl
- or NO
3-.
When CCCP or DNP was added to the cell suspension in the dark, an uptake of H
+ into the cells followed. The H
+ uptake in the dark on the addition of CCCP or DNP also required the presence of Cl
- or NO
3-.
Direct measurement of
36Cl
- translocation showed that Cl
- is accumulated into the cells with H
+ in the dark after the addition of CCCP.
These results suggest that the H
+ movement couples with anion movement and that the transport of anions is the determining factor for the direction and magnitude of H
+ flux.
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