Molecular cloning and chromosomal mapping of the human gene for the testis-specific catalytic subunit of calmodulin-dependent protein phosphatase (calcineurin A)

A cDNA for an alternatively spliced variant of the testis-specific catalytic subunit of calmodulin dependent protein phosphatase (CaM-PrP) was cloned from a human testis library. The nucleotide sequence of 2134 base pairs (bp) encodes a protein of 502 amino acids (Mr ≈57,132) and pI 7.0. The cDNA sequence differs from the murine form of this gene by a 30 by deletion in the coding region, the position of which matches those in the two other genes for the catalytic subunit. These data indicate that this alternative splicing event arose prior to the divergence of the three genes. The deduced sequence of the human protein is only 88% identical to the homologous murine form, in striking contrast to the other two CaM-PrP catalytic subunits which are highly conserved between mouse and human (≈99%); this indicates a more rapid rate of evolution for the testis-specific gene. Analysis of Southern blots containing DNA from human hamster somatic cell hybrids show that the gene is on human chromosome 8.