Identification of a Giα Binding Site on Type V Adenylyl Cyclase

• DOI: 10.1074/jbc.273.40.25831
• Publication Date: 2002-07-26T15:02:22Z
• Authors: Carmen W. Dessauer; John J.G. Tesmer; Stephen R. Sprang; Alfred G. Gilman
• Keywords: ADCY3; ADCY10

The stimulatory G protein α subunit G_sα binds within a cleft in adenylyl cyclase formed by the α1-α2 and α3-β4 loops of C₂ domain. pseudosymmetry C₁ domains suggests that homologous inhibitory G_iα could bind to analogous C₁. We demonstrate myristoylated guanosine 5′-3-<i>O</i>-(thio)triphosphate-G_iα1 forms stable complex with (but not C₂) domain type V cyclase. Mutagenesis membrane-bound enzyme identified residues whose alteration either increased or substantially decreased IC₅₀ for inhibition G_iα1. These mutations suggest binding α2 α3 helices C₁, site C₂. Adenylyl activity reconstituted mixture was also inhibited G_iα. C_1b contributed affinity G_iα, but source had little effect. Mutations this soluble system faithfully reflected phenotypes observed enzyme. pseudosymmetrical structure permits bidirectional regulation subunits.