Human testis cDNA for the regulatory subunit RIIα of CAMP‐dependent protein kinase encodes an alternate amino‐terminal region

Abstract

Phosphorylations catalysed by cAMP-dependent protein kinase are essential for sperm motility, and type II cAMP-dependent protein kinase in mature sperm has been shown to be firmly bound to the flagellum via the regulatory subunit, RII. The present study documents high-levelled expression of a human, testis-specific RIIα mRNA (2.0 kb) analogous to the rat mRNA which is induced in haploid germ cells [(1988) FEBS Lett. 229, 391–394]. We report the molecular cloning of a full-length human cDNA corresponding to this unique testis mRNA, and the presence of an alternate amino-terminal region (amino acids 45–75) of the predicted RIIα protein (404 amino acids) compared with the previously published mouse and rat sequences. However, this alternate region is also shown to be present in RIIα mRNA (7.0 kb) of human somatic cells. Our data indicate the divergent amino-terminal sequence to be due to species differences, suggesting an active evolutionary pressure on this particular region, which could be involved in subcellular attachment of RIIα and thereby localization of kinase activity to certain targets within the cell