Protein Phosphatase 3, Catalytic Subunit Beta Isoform (PPP3Cb)

Calcineurin, a calmodulin-regulated protein phosphatase, is found in the cells of all eukaryotes ranging from yeast to mammals. Wang et al. (1996) described this heterodimeric protein as having a 19-kD Ca(2+)-binding regulatory subunit, calcineurin B, and a 58- to 59-kD catalytic subunit, calcineurin A. One gene encodes calcineurin B (PPP3R1) in all tissues except testis, and it is highly conserved at the level of both protein and DNA sequences in eukaryotes. In contrast, there are 2 major isoforms, alpha (PPP3CA) and beta (PPP3CB), of calcineurin A encoded by separate genes located on different human chromosomes. A third isoform, A-gamma (PPP3CC), is unique to testis. Additional diversity of calcineurin A is created by alternative splicing of mRNAs.