OLFACTORY ADENYLYL CYCLASE - IDENTIFICATION AND PURIFICATION OF A NOVEL ENZYME FORM

Abstract

Rat olfactory adenylyl cyclase has been identified by means of a monoclonal antibody BBC-2, which reacts with both Ca2+/calmodulin-sensitive and -insensitive forms of adenylyl cyclase (Mollner, S., and Pfeuffer, T. (1988) Eur. J. Biochem. 171, 265-271). The antibody recognized a 180-kDa polypeptide in olfactory cilia but not in decilitated olfactory epithelial membranes. A protein of the same mobility was observed when olfactory adenylyl cyclase was purified by forskolin-agarose affinity chromatography followed by radioiodination. Its identity was further established by cross-linking to [32P]ADP-ribosylated GS.alpha. (GTP-binding protein), to yield a single radiolabelled product of Mr .apprx. 220. Olfactory adenylyl cyclase has a .apprx.3-fold higher turnover number, as assessed from stoichiometric binding of [35S]guanosine 5''-(3-O-thio)triphosphate. Therefore, the considerably higher specific adenylyl cyclase activity in olfactory cilia must be due to a .apprx. 100-fold higher molar concentration of enzyme in this tissue.