Genetically tailored atrial natriuretic factor-dependent guanylate cyclase Immunological and functional identity with 180 kDa membrane guanylate cyclase and ATP signaling site

Abstract

Biochemical and immunological studies have established that one of the signal transducers of atrial natriuretic factor (ANF) is a 180 kDa membrane guanylate cyclase (180 kDa mGC), which is also an ANF receptor; obligatory in the transduction process is an intervening ATP-regulated step, but its mechanism is not known. GCα is a newly discovered member of the guanylate cyclase family whose activity is independent of the known natriuretic peptides, and the enzyme is not an ANF receptor. The genetically tailored GCα, GCα-DmutGln 338 Leu 364, however, is not only a guanylate cyclase but also an ANF receptor and is structurally and functionally identical to the cloned wild-type ANF receptor guanylate cyclase, GC-A. We now report that the ANF-dependent guanylate cyclase activity in the particulate fractions of cells transfected with GCα-DmutGln 338 Leu 364 was inhibited by the 180 kDa mGC polyclonal antibody, and with this antibody probe it was possible to purify the 130 kDa expressed receptor; the hormone-dependent cyclase activity of this receptor was exclusively dependent upon ATP; and through site-directed mutational studies with GCα mutants, the signaling sequence that defines ATP binding site was identified. We thus conclude that 180 kDa mGC and the mutant protein are immunologically similar; both proteins are linked to the ANF signal in the generation of cyclic GMP synthesis; and in both the ligand binding and catalytic activities are bridged through a defined ATP binding module.