Y. Hong et al., EXPRESSION OF 3 MEMBERS OF THE CALCIUM-DEPENDENT PROTEIN-KINASE GENE FAMILY IN ARABIDOPSIS-THALIANA, Plant molecular biology, 30(6), 1996, pp. 1259-1275
Calcium-dependent protein kinases (CDPKs) belong to a unique family of
enzymes containing a single polypeptide chain with a kinase domain at
the amino terminus and a putative calcium-binding EF hands structure
at the carboxyl terminus. From Arabidopsis thaliana, we have cloned th
ree distinct cDNA sequences encoding CDPKs, which were designated as a
tcdpk6, ntcdpk9 and atcdpk19. The full-length cDNA sequences for atcdp
k6, atcdpk9 and atcdpk19 encode proteins with a molecular weight of 59
343, 55376 and 59947, respectively. Recombinant at CDPK6 and at CDPK9
proteins were fully active as kinases whose activities were induced by
Ca2+. Biochemical studies suggested the presence of an autoinhibitory
domain in the junction between the kinase domain and the EF hands str
ucture. Serial deletion of the four EF hands of at CDPK6 demonstrated
that the integrity of the four EF hands was crucial to the Ca2+ respon
se. All the three atcdpk genes were ubiquitously expressed in the plan
t as demonstrated by RNA gel blot experiments. Comparison of the genom
ic sequences suggested that the three cdpk genes have evolved differen
tly. Using antibodies against at CDPK6 and at CDPK9 for immunohistoche
mical experiments, CDPKs were found to be expressed in specific cell t
ypes in a temporally and developmentally regulated manner.