CDNA CLONING AND SEQUENCE-ANALYSIS OF THE BOVINE ADRENOCORTICOTROPIC HORMONE (ACTH) RECEPTOR

We isolated five independent cDNAs of nearly 3000 bp for the bovine AC TH receptor by screening adrenal cortex cDNA libraries with a PCR clon ed cDNA fragment. The deduced receptor sequence includes 297 residues (M(r) = 33 258) with 81% identity with the human ACTH receptor, and sh ows seven hydrophobic transmembrane domains. The calculated M(r) of th e receptor is smaller than the 40-45 kDa observed in crosslinking stud ies with labeled ACTH. Since the bovine and human receptors have two g lycosylation motifs in the N-terminus, the difference may result from glycosylation of the receptor. Analysis of the sequences of both bovin e and human receptors revealed a single protein kinase A phosphorylati on motif located in the third intracellular loop (Ser-209) juxtaposed to a protein kinase C phosphorylation motif (Thr-204). Thus, the invol vement of protein kinase A and C pathways in ACTH action may be mediat ed in part by phosphorylation of the ACTH receptor at these motifs. Th e 3'-untranslated region of the bovine cDNA is > 2000 bp and includes two inverse repeats giving an extensive and strong secondary structure to the ACTH receptor RNA.