Proton translocation in chloroplasts and its relationship to electron transport between the photosystems
Using dark adapted isolated spinach chloroplasts and sequences of brief saturating flashes the correlation of the uptake and release of protons with electron transport from Photosystem II to Photosystem I were studied. Flash induced proton uptake shows a weak, damped binary oscillation, with maxima occurring after the 2nd, 4th, etc., flashes. The damping factor is comparable to that observed in the O/sub 2/ flash yield oscillation and therefore explained by misses in Photosystem II. Flash induced proton release inside the chloroplast membrane shows a strong damped binary oscillation with maximum release occurring also after the 2nd, 4th, etc. flashes. This phenomenon is correlated with the earlier reported binary oscillations of electron transport and shows that both electrons and protons are transported in pairs between the photosystems. In two sequential flashes 4H/sup +/ from the outside of the thylakoid and 2e/sup -/ from water are accumulated at a binding site B. Subsequently, the two electrons are transferred to non-protonated acceptors in Photosystem I (probably plastocyanin and cytochrome f) and the 4H/sup +/ are released inside the thylakoid. It is concluded that a primary proton transporting site and/or energy conserving step located between the photosystems is being observed.
- Research Organization:
- Martin Marietta Labs., Baltimore, Md. (USA)
- OSTI ID:
- 7141840
- Report Number(s):
- COO-3326-48
- Country of Publication:
- United States
- Language:
- English
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