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Ca 2+ ‐dependent in vitro phosphorylation of soluble proteins from germinating wheat ( Triticum turgidum ) endosperm
Author(s) -
Krishnan Hari B.,
Pueppke Steven G.
Publication year - 1988
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1988.tb06374.x
Subject(s) - phosphorylation , endosperm , serine , protein kinase a , biochemistry , protein phosphorylation , kinase , threonine , in vitro , phosphopeptide , biology , chemistry , microbiology and biotechnology
A 40000 g supernatant fraction from extracts of germinating wheat ( Triticum turgidum Desf. cv. Edmore) endosperm contains protein kinase activity that phosphorylates several endogenous proteins. In vitro incorporation of radiolabel from [ 32 P]‐ATP into phosphoproteins was maximal in the presence of 1 m M CaCl 2 and 5 m M MgCl 2 Ca 2+ at micromolar concentrations greatly stimulated the phosphorylation of 49 and 47 kDa polypeptides and also inhibited the phosphorylation of a few specific polypeptides. The phosphorylation of the 49 and 47 kDa polypeptides was present at 2 days after seed germination and was maximal at 8 days. Quantitative protein changes were also detected during the seed germination, but differences could not be correlated with changes in protein phosphorylation. Phosphoamino acid analysis by two dimensional thin‐layer electrophoresis showed that the Ca 2+ ‐dependent protein kinase phosphorylates a serine residue of the 47 kDa polypeptide. Ca 2+ ‐dependent protein kinase phosphorylates a serine residue of the 47 KDa polypeptide. Ca 2+ dependent protein phosphorylktion was inhibited by phenothiazine‐derived drugs. Addition of S‐adenosylmethionine to the in vitro phosphorylation reaction specifically inhibited the Ca 2+ ‐dependent protein phosphorylation.