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Regulation of phosphorylation of chloroplast membrane polypeptides by the redox state of plastoquinone
Author(s) -
Horton Peter,
Allen John F.,
Black Michael T.,
Bennett John
Publication year - 1981
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(81)80716-8
Subject(s) - plastoquinone , library science , biological sciences , chemistry , chloroplast , biology , biochemistry , computer science , thylakoid , computational biology , gene
Higher plant chloroplasts possess a light-activated protein kinase that catalyses phosphorylation of several thylakoid proteins including LHCP [l-5]. A decrease in the yield of chlorophyll fluorescence from PSI1 at room temperature was caused by addition of ATP under conditions necessary for kinase activity. Under the same conditions there is an increase in the relative fluorescence emission from PSI at -196°C. These observations support the proposal that phosphorylation of LHCP controls the distribution of quanta between PSI1 and PSI [6,7]. On the basis of the ability of various partial reactions of photosynthetic electron transport to promote kinase activity, it was proposed that the redox state of plastoquinone controls protein phosphorylation and hence also the distribution of quanta [8]. A similar suggestion was made to explain ATP-induced fluorescence quenching [7] and potentiometric redox titration indeed showed the involvement of a 2 electron carrier with E,, 7.8 -Ok+50 mv [9]. However, it remained to be shlwn that: (i) Phosphorylation was responsible for the fluorescence changes, (ii) Plastoquinone in pea chloroplasts titrates with this midpoint potential. Here, the crucial links are established between the redox state of plastoquinone, the activation of protein kinase and changes in chlorophyll fluorescence. A model by which the redox state of plastoquinone can control the relative rates of excitation of PSI1 and PSI is presented.