Molecular cloning of hippocalcin, a novel calcium-binding protein of the recoverin family exclusively expressed in hippocampus.

We have isolated a cDNA clone encoding a novel calcium-binding protein of the recoverin family from rat brain cDNA library. This clone (PCB11) has 588 nucleotides in the open reading frame including the termination codon, 174 nucleotides of the 5' leader and 800 nucleotides of the 3' noncoding region. The complete amino acid sequence deduced from the cDNA is composed of 195 residues, has a calculated molecular mass of 22,574 Daltons, and contains three putative calcium-binding domains of the EF-hand structure. The deduced amino acid sequence has a striking sequence homology to those of the retinal recoverin family (recoverin, visinin, P26, 23kD protein, S-modulin) and the brain-derived recoverin family (P23k, 21-kDa CaBP and neurocalcin). Northern blot, in situ hybridization, immunoblot and immunohistochemical analyses revealed that the protein is exclusively expressed in pyramidal layer of the hippocampus. The protein was therefore designated hippocalcin.