Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
A novel adenylylcyclase cDNA (type V) was isolated from a canine heart cDNA library. Northern blotting indicates that the expression of this message is most abundant in heart with a lesser amount in brain but is absent in a variety of other tissues including lung, kidney, skeletal muscle, lymphocyte, and testis. The putative protein product predicted from the cDNA sequence has the motif of tandem six-transmembrane spans separated by a large hydrophilic cytoplasmic loop as seen in other members of the adenylylcyclase family. When this protein is expressed using a CMT cell transient expression system, the adenylylcyclase activity was stimulated by NaF, GTP gamma S, and forskolin, but not by calmodulin. The activity was inhibited in a concentration-dependent manner with either P-site active agents such as adenosine or in the presence of calcium. These data indicate that the protein encoded by this cDNA is adenylylcyclase with the biochemical features characteristic of the cardiac isoform.