Inhibition of the light-induced H+ release from uncoupled thylakoid membranes by N-ethylmaleimide.
The light-induced H+ release from thylakoids, which can be observed under completely uncoupled conditions, was inhibited by the SH reagent N-ethylmaleimide (NEM) and its analogs, while the conventional H+ uptake and electron transfer were not affected. The half-inhibiting concentration of NEM for the H+ release was 10 mM and 4 mM in thylakoids in the presence of nigericin and in CF1-depleted thylakoids, respectively. The inhibitory effect increased with the increase in hydrophobicity of the NEM analogs: N-methylmaleimide less than N-ethylmaleimide less than N-phenylmaleimide. It is suggested that SH groups in hydrophobic interior within the membrane are essential to the release of protons.
Yamasaki
H
H
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
Okayama
S
S
Shibata
M
M
Nishimura
M
M
D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D008301:Maleimides / Q000494:pharmacology; D010944:Plants / Q000378:metabolism
D008301:Maleimides; D005033:Ethylmaleimide