Ubiquitous and bifunctional 180 kDa atrial natriuretic factor-dependent guanylate cyclase

Original studies with rat adrenocortical carcinoma identified a 180 kDa cell-surface protein which contained both guanylate cyclase and atrial natriuretic factor (ANF) receptor, representing a potentially new type of bifunctional receptor protein. It is both a receptor and a guanylate cyclase. This critical conclusion of bifunctionality was based on the observation that the pure 180 kDa protein, whose purity was established by protein staining of the denatured gels, contained both the ligand binding and guanylate cyclase activities. Utilizing the antibody to 180 kDa membrane guanylate cyclase (180 kDa mGC), we now (i) report the complete purification of 180 kDa mGC from rat testes; (ii) demonstrate by affinity cross-linking studies that the homogeneous 180 kDa protein isolated from rat testes and adrenal gland binds ANF and (iii) show that bovine aortic endothelial cell membranes contain the 180 kDa mGC that is ANF-dependent in the production of cyclic GMP. These results validate the conclusion of the bifunctionality, ubiquity, and the general linkage to the ANF-dependent generation of cyclic GMP signal of this protein.