Using
protein sequence data obtained from a
calcium- and
phospholipid-regulated
protein kinase purified from maize (Zea mays), we isolated a
cDNA encoding a
calcium-dependent protein kinase (CDPK), which we designated ZmCPK11. The deduced amino acid sequence of ZmCPK11 includes the sequences of all the
peptides obtained from the native
protein. The ZmCPK11 sequence contains the
kinase, autoregulatory, and
calmodulin-like domains typical of CDPKs. Transcripts for ZmCPK11 were present in every tested organ of the plant, relatively high in seeds and seedlings and lower in stems, roots, and leaves. In leaves,
kinase activity and ZmCPK11
mRNA accumulation were stimulated by wounding. The level of ZmCPK11 is also increased in noninjured neighboring leaves. The results suggest that the maize
protein kinase is involved in a systemic response to wounding. Bacterially expressed
glutathione S-transferase (GST)-ZmCPK11 was catalytically active in a
calcium-dependent manner. Like the native
enzyme, GST-ZmCPK11 was able to phosphorylate
histone III-S and Syntide 2. Phosphorylation of
histone was stimulated by
phosphatidylserine,
phosphatidylinositol, and
phosphatidic acid, whereas
phosphatidylcholine,
lysophosphatidylcholine,
phosphatidylethanolamine,
diolein, and
cardiolipin did not increase the enzymatic activity. Autophosphorylation of GST-ZmCPK11 was stimulated by
calcium and by
phosphatidic acid and, to a lesser extent, by
phosphatidylserine.
Phosphatidylcholine did not affect autophosphorylation. These data unequivocally identify the maize
phospholipid- and
calcium-regulated
protein kinase, which has
protein kinase C-like activity, as a CDPK, and emphasize the potential that other CDPKs are regulated by
phospholipids in addition to
calcium.