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Increase in the level of thylakoid protein phosphorylation in maize mesophyll chloroplasts by decrease in the transthylakoid pH gradient
Author(s) -
Fernyhough P.,
Foyer C.H.,
Horton P.
Publication year - 1984
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(84)80927-8
Subject(s) - nigericin , plastoquinone , phosphorylation , chloroplast , protein phosphorylation , photosystem ii , thylakoid , dcmu , biophysics , protein kinase a , biochemistry , chlorophyll , photosystem i , photosynthesis , chemistry , biology , botany , membrane , gene
Phosphorylation of the light‐harvesting chlorophyll protein (LHCP) has been measured in intact chloroplasts prepared from maize mesophyll protoplasts. Maximum levels of phosphorylation were obtained in the absence of added reducible photosynthetic substrate and the presence of low concentrations of the ΔpH dissipating ionophore, nigericin. Assays of chlorophyll fluorescence indicated a high reduction level of plastoquinone under these conditions. It is suggested that the size of the transthylakoid pH gradient exerts control over the redox activation of the protein kinase and that protein phosphorylation is involved in the regulation of cyclic and non‐cyclic electron flow. Further evidence for this view was obtained from stimulation of protein phosphorylation by pyruvate which lowers ΔpH by ATP consumption and by inhibition of phosphorylation in strong light and by low levels of DCMU.