Open AccessA calcium and calmodulin‐dependent protein kinase present in differentiating Dictyostelium discoideum
Author(s) -
Dunbar Andrew J.,
Wheldrake John F.
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06623.x
Subject(s) - dictyostelium discoideum , calmodulin , protein kinase a , biochemistry , biology , kinase , enzyme , chemistry , gene
A protein kinase from Dictyostelium discoideum which phosphorylates the synthetic peptide, calmodulin‐dependent protein kinase substrate (CDPKS, amino acid sequence: PLRRTLSVAA) and is stimulated by Ca 2+ /calmodulin is described. This is the first report of a protein kinase with these characteristics in D. discoideum . The enzyme was partially purified by Q‐Sepharose chromatography. The protein kinase is very labile, and rapidly loses Ca 2+ /calmodulin‐dependence upon standing at 4°C, even in the presence of protease inhibitors, making further purification and characterisation difficult. In the active fractions, a 55 kDa polypeptide is labelled with [γ‐ 32 P]ATP in vitro under conditions in which intramolecular rather than intermolecular reactions are favoured. The phosphorylation of this peptide is stimulated in the presence of Ca 2+ and calmodulin but not Ca 2+ alone. Ca 2+ /calmodulin‐dependent stimulation is inhibited in the presence of the calmodulin antagonist, trifluoperazine (TFP). It is proposed that the 55 kDa polypeptide may represent the autophosphorylated form of the enzyme.