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Uni‐site ATP synthesis in thylakoids
Author(s) -
Labahn Andreas,
Fromme Petra,
Gräber Peter
Publication year - 1990
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(90)80385-v
Subject(s) - thylakoid , atp synthase , chemiosmosis , chemistry , atp synthase gamma subunit , dithiothreitol , enzyme , biochemistry , nucleotide , adenosine triphosphate , f atpase , biophysics , atpase , biology , atp hydrolysis , chloroplast , gene
Uni‐site ATP synthesis was measured with thylakoids. The membrane‐bound ATP‐synthase, CF 0 F 1 was brought into the active, reduced state by illumination in the presence of thioredoxin, dithiothreitol and phosphate. This enzyme contains two tightly bound ATP per CF o F 1 . ATP was released from the enzyme when ADP was added in substoichiometric amounts during illumination. Experiments with [ 14 C]ADP indicated that after binding the same nucleotide was phosphorylated and released as [ 14 C]ATP, i.e. only one site is involved in ATP‐synthesis (uni‐site ATP‐synthesis'). The two tightly bound ATP are not involved in the catalytic turnover. The rate constant for ADP binding was (4 ± 2) × 10 6 M −1 s −1 . Compared to deenergized conditions the rate constant for ADP binding and that for ATP‐release were drastically increased, i.e. membrane energization increased the rate constants for the ATP‐synthesis direction.