Molecular cloning and expression of a novel type V adenylyl cyclase from rabbit myocardium

A cDNA of a novel form of type V adenylyl cyclase has been cloned from rabbit myocardium using oligonucleotide probes derived from peptides that were produced by enzymatic cleavage of purified heart cyclase. A corresponding mRNA (6 kb) has been detected in rabbit myocardial tissue by Northern blot analysis. The cDNA encodes a protein of 1,264 amino acids exhibiting 12 putative membrane-spanning regions in its hydrophilicity profile. Sequence comparison to two other previously published type V adenylyl cyclase reveals amino-terminal domains of different length and low correlative homology, whereas the rest of the sequences is almost identical. The nonconserved amino-terminal region of the subtype consists of 214 amino acids and exceeds the length of the others by 40 and 80 residues, respectively. Its presence in membrane preparations from different tissues has been confirmed immunologically using an antibody directed against a synthetic peptide. The cloned adenylyl cyclase was functionally expressed in COS-1 cells to attain an enzymatic activity 3.5- to 14-fold above control in the presence of forskolin.