Substrate specificity of wheat embryo calcium-dependent protein kinase

AbstractWheat embryo Ca2+ -dependent protein kinase (CDPK) phosphorylates a variety of synthetic peptides having a Basic-X-X-Ser sequence but peptides with a Basic-Basic-X-Ser(Thr) sequence are relatively poor substrates. Wheat germ CDPK phosphorylates a variety of proteins of which histone H1 and bovine serum albumin are among the better substrates. A single phosphorylated tryptic peptide was purified from bovine histone H1 phosphorylated by wheat embryo CDPK and subjected to Edman degradation yielding the sequence Gly97-Thr-Gly-Ala-Ser-Gly-Ser(PO4)-Phe-Lys105. Ser103 on bovine histone H1 is also the residue phosphorylated by rat brain protein kinase C