Isolation and sequence of rat testis cdna for a calcium binding polypeptide similar to the regulatory subunit of calcineurin

We have cloned and sequenced rat testis cDNAs coding for a calcium binding polypeptide similar to calcineurin β subunit, the Ca²⁺-binding subunit of the Ca²⁺/calmodulin stimulated protein phosphatase. Rat testis cDNA library was screened with a monoclonal antibody Va1 raised against bovine brain calcineurin β subunit. The deduced amino acid sequence is similar to that of human brain calcineurin β subunit with respect to containing four putative calcium binding sites. However, distinct differences were found: 1) The cloned cDNA had six amino acids polypeptide tail at carboxy-terminal which is absent in human brain calcineurin β subunit. This amino acids tail makes the carboxy-terminal highly hydrophilic in contrast to the human brain β subunit which is hydrophobic at carboxy-terminal; 2) eleven amino acids at the N-terminal of the cloned cDNA were completely different from the corresponding region of the brain calcineurin β subunit.