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Studies on the proton release pattern of the donor side of system II
Author(s) -
Renger G.,
Voelker M.
Publication year - 1982
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(82)81101-0
Subject(s) - proton , chemistry , thylakoid , tris , kinetics , electron transport chain , electron , excitation , proton transport , photochemistry , chloroplast , analytical chemistry (journal) , chromatography , biochemistry , physics , quantum mechanics , gene
The protonization pattern of the endogenous donor component D 1 which feeds electrons directly into chl‐ a + II has been analyzed in Tris‐washed inside‐out thylakoids with the aid of appropriate pH‐indicators. It was found that under repetitive flash excitation the amount of protons released is proportional to the extent of D 1 ‐oxidation, depending on the time between the flashes. The kinetics of D 1 ‐oxidation (being practically the same as in normal Tris‐washed chloroplasts) are faster than the proton release by two orders of magnitude. The results lead to the conclusion that D 1 is protonized in the reduced state with p K (D ox 1 ) < 5 and becomes deprotonized in the oxidized state with p K (D red 1 ) ≳ 8. The proton release is kinetically limited by a transport barrier. Implications on the interpretation of the proton release pattern in preparation with intact water oxidation are discussed.