Multiplicity in type V adenylylcyclase: type V-a and type V-b.

Type V mammalian adenylylcyclase cDNA was originally isolated from two animal species, the dog and rat. The amino acid sequences from the two species are highly homologous, but completely different in the putative N-terminal, cytoplasmic region. Northern blot analysis using oligonucleotide probes unique to either of the two clones has revealed that the two forms of type V adenylylcyclase mRNA, canine form (= type V-a) and rat form (= type V-b), are co-expressed as splicing variants in both species. Genomic Southern blot analysis has suggested that the two forms are the products of a single gene. When overexpressed, however, deletion of the N-terminal domain did not alter any biochemical properties. Thus multiple splicing variants with unique N-terminal amino acid sequences of type V adenylylcyclase can be generated from a single gene, however, biochemical properties of these variants may not be different.