title: Pertussis toxin inhibits cAMP surface receptor-stimulated binding of [35S]GTP gamma S to Dictyostelium discoideum membranes.
abstract: GTP-binding activity to Dictyostelium discoideum membranes was investigated using various guanine nucleotides. Rank order of binding activities was: GTP gamma S greater than GTP greater than 8-N3-GTP; the binding of GTP gamma S and GTP, but not of 8-N3-GTP, was stimulated by receptor agonists. [3H]GTP binding to D. discoideum membranes has been described previously by a single binding type (Kd = 2.6 microM, Bmax = 85 nM). More detailed studies with [35S]GTP gamma S showed heterogeneous binding composed of two forms of binding sites with respectively high (Kd = 0.2 microM) and low (Kd = 6.3 microM) affinity. cAMP derivatives enhanced GTP gamma S binding by increasing the affinity and the number of the high-affinity sites, while the low-affinity sites were not affected by cAMP. The specificity of cAMP derivatives for stimulation of GTP gamma S binding showed a close correlation with the specificity for binding to the cell surface cAMP receptor. Pretreatment of D. discoideum cells with pertussis toxin did not affect basal GTP and GTP gamma S binding, but eliminated the cAMP stimulation of GTP and GTP gamma S binding. These results indicate that D. discoideum cells have a pertussis toxin-sensitive GTP-binding protein that interacts with the surface cAMP receptor, suggesting the functional interaction of surface receptor with a G-protein in D. discoideum.
authors.affiliation: Cell Biology and Genetics Unit, Zoological Laboratory, Leiden, The Netherlands.
authors.forename: B E
authors.initials: BE
authors.lastname: Snaar-Jagalska
authors.forename: R J
authors.initials: RJ
authors.lastname: De Wit
authors.forename: P J
authors.initials: PJ
authors.lastname: Van Haastert
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D004023:Dictyostelium / Q000187:drug effects / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D007700:Kinetics; D037342:Pertussis Toxin; D011953:Receptors, Cyclic AMP / Q000502:physiology*; D013873:Thionucleotides / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D006150:Guanine Nucleotides; D011953:Receptors, Cyclic AMP; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D037342:Pertussis Toxin