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Are guanine nucleotide‐binding proteins involved in regulation of thylakoid protein kinase activity?
Author(s) -
Millner Paul A.
Publication year - 1987
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(87)80570-7
Subject(s) - thylakoid , guanosine , gtp' , biochemistry , guanine , nucleotide , spinach , protein kinase a , biology , kinase , chemistry , chloroplast , enzyme , gene
The slow ATP‐induced decrease in chlorophyll fluorescence associated with the phosphorylation of LHC II seen in spinach thylakoids was inhibited by GTP and its non‐hydrolysable analogues β, γ‐imidoguanosine 5′‐triphosphate and guanosine 5′‐ O ‐(3‐thiotriphosphate), but not by other nucleotide triphosphates or diphosphates. Inhibition by guanosine 5′‐ O ‐(3‐thiotriphosphate) appeared to require prior exposure of the thylakoid membranes to the guanine nucleotide under conditions where the protein kinase was active but unable to turnover. Binding studies with thylakoid membranes using [5′,8‐ 3 H]GTP or [ 35 S]guanosine 5′‐ O ‐(3‐thiotriphosphate) show that under similar conditions an increase in specific binding of these radiolabelled nucleotides occurs. The data presented provide evidence for the existence of a guanine nucleotide‐binding regulatory protein that is able to interact with the thylakoid protein kinase.