Calcium Binding Tyrosine Phosphorylation Regulated Protein (CABYR)

The full-length CABYR transcript encodes a 493-amino acid protein with a calculated molecular mass of 52.8 kD that is translated entirely from coding region A. It has an N-terminal domain homologous to the dimerization and AKAP-binding domains of the RII-alpha subunit of cAMP-dependent kinase (PRKAR2A), an EF-hand-like motif for calcium binding, 7 putative tyrosine phosphorylation sites, and 5 PxxP motifs for interaction with SH3 domains. The remaining 3 CABYR variants encode proteins translated from portions of coding region A and all or part of coding region B.CABYR transcripts of 2.4 and 1.4 kb in testis only, and RNA dot blot analysis confirmed testis-specific expression. Immunofluorescence analysis revealed CABYR in round and elongated spermatids and spermatozoa.