Dictyostelium discoideum mutant synag 7 with altered G-protein-adenylate cyclase interaction.
Previous results have shown that Dictyostelium discoideum mutant synag 7 is defective in the regulation of adenylate cyclase by receptor agonists in vivo and by GTP gamma S in vitro; the guanine nucleotide activation of adenylate cyclase is restored by the high-speed supernatant from wild-type cells. Here we report that in synag 7 membranes: (1) cyclic AMP receptors had normal levels and were regulated by guanine nucleotides as in wild-type; (2) GTP binding and high-affinity GTPase were reduced but still stimulated by cyclic AMP; (3) the supernatant from wild-type cells restored GTP binding to membranes of this mutant, and partly restored high-affinity GTPase activity; (4) the supernatant of synag 7 was ineffective in these reconstitutions and did not influence GTP binding and GTPase activities in mutant or wild-type membranes. These results suggest that the defect in mutant synag 7 is located between G-protein and adenylate cyclase, and not between receptor and G-protein. A factor in the supernatant is absent in synag 7 and appears to be essential for normal GTP binding, GTPase and activation of adenylate cyclase. This soluble heat-labile factor may represent a new molecule required for receptor- and G-protein-mediated activation of adenylate cyclase.
Snaar-Jagalska
B E
BE
Zoological Laboratory, University of Leiden, The Netherlands.
Van Haastert
P J
PJ
D000262:Adenylyl Cyclases / Q000378:metabolism*; D004023:Dictyostelium / Q000201:enzymology / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D009154:Mutation
D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases