Cloning of a cDNA encoding a new calcium-binding protein from Dictyostelium discoideum and its developmental regulation.

By employing 2D-PAGE, a protein differentially expressed during the development of Dictyostelium discoideum was discovered. The full cDNA of this protein was cloned using RT-PCR. The deduced protein is composed of 166 amino acid residues containing four EF-hand domains typical for calcium-binding proteins and was named CBP3. This protein shows little amino acid sequence homology with the other calcium-binding proteins from D. discoideum except EF-hand domains. The CBP3 mRNA was absent in vegetative amebas and accumulated maximally at 6 h of the development on filters. The mRNA level decreased thereafter and disappeared after 12 h of the development, while the protein level peaked at 8 h of development and remained constant thereafter. The mobility of CBP3 on SDS gel was shifted by treatment with EGTA, confirming the Ca2+-binding activity of the protein.