Plant calcium-dependent protein kinase-related kinases (CRKs) do not require calcium for their activities.
In plants, calcium-dependent protein kinases (CDPKs) make up a large family that is characterized by a C-terminal calmodulin(CaM)-like domain. Recently, a novel carrot cDNA clone encoding an atypical CDPK, which has a significantly degenerate sequence in the CaM-like domain, was found and named CDPK-related protein kinase (CRK) [Lindzen, E. and Choi, J.H. (1995) Plant Mol. Biol. 28, 785-797]. We obtained two different cDNA clones from maize which encode CRKs. For the first enzymatic characterization of CRK, a maize cDNA clone was expressed in E. coli. The recombinant protein efficiently phosphorylated casein, a conventional protein substrate. Notably, in this in vitro phosphorylation assay, the kinase activity did not require calcium as an activator. Thus, CRKs were suggested to be novel calcium-independent protein kinases having a degenerate CaM domain, the function of which remains to be elucidated.
Laboratory of Applied Botany, Faculty of Agriculture, Kyoto University, Sakyo-ku, Japan.
T
T
Furumoto
N
N
Ogawa
S
S
Hata
K
K
Izui
D000595:Amino Acid Sequence; D002118:Calcium / Q000494:pharmacology*; D002364:Caseins / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018552:Daucus carota / Q000201:enzymology; D004533:Egtazic Acid / Q000494:pharmacology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010802:Phylogeny; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics
D002364:Caseins; D018076:DNA, Complementary; D011994:Recombinant Proteins; D004533:Egtazic Acid; D011494:Protein Kinases; D002118:Calcium