Dictyostelium discoideum contains a family of calmodulin‐related EF‐hand proteins that are developmentally regulated

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Abstract
A full‐length genomic DNA fragment that codes for a novel EF‐hand protein from Dictyostelium discoideum was cloned and sequenced. The protein is composed of 168 amino acids and contains four consensus sequences that are typical for Ca2+‐binding EF‐hand domains. The protein sequence exhibits only minor similarities to other calmodulin‐type proteins from Dictyostelium. The genomic DNA harbors two short introns; their positions suggest that the gene is unrelated to the EF‐hand proteins from the calmodulin group. Northern blot analysis showed that the mRNA level was significantly increased during development. Polyclonal antibodies raised against the recombinant protein recognized in Western blots a protein of about 20 kDa. Like the mRNA, also the protein was more abundant in developing cells. Overlay experiments with 45Ca2+ indicated that the EF‐hands in fact have Ca2+‐binding activity. The recent description of CBP1, another calmodulin‐type Dictyostelium protein that is upregulated during development [Coukell et al. (1995) FEBS Lett. 362, 342–346], suggests that D. discoideum contains a family of EF‐hand proteins that have specific functions during distinct steps of development. We therefore designate the protein described in this report as CBP2.