Guanine nucleotide regulation of [3H]vasopressin binding to liver plasma membranes and solubilized receptors. Evidence for the involvement of a guanine nucleotide regulatory protein.
A guanine nucleotide regulatory protein may be involved in vasopressin-receptor-mediated polyphosphoinositide breakdown in rat liver. Therefore we examined the effects of the non-hydrolysable guanine nucleotide guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG) on [3H]vasopressin ([3H]AVP) binding to hepatic plasma membranes and detergent extracts. [3H]AVP bound to a single set of high-affinity binding sites in membranes. Addition of p[NH]ppG decreased the affinity of receptor binding without altering the maximal binding capacity. The rate of dissociation of [3H]AVP from membrane-bound receptors was also enhanced by p[NH]ppG. Solubilization of [3H]AVP-prelabelled membranes with dodecyl beta-D-maltoside resulted in a [3H]AVP-receptor complex that was unstable in solution. Incubation of these extracts for 5 min at 30 degrees C resulted in a 40% loss of bound [3H]AVP, whereas in the presence of p[NH]ppG there was a 54% loss. However, when membranes were prelabelled with [3H]AVP and p[NH]ppG and then solubilized, the resulting hormone-receptor complex was still temperature-labile but insensitive to the further addition of p[NH]ppG. The molecular size of soluble vasopressin receptors was estimated by gel filtration. The [3H]AVP-receptor complex was eluted as a single peak with an apparent molecular size of 258 kDa. However, no peak was detected when solubilized extract was made from membranes prelabelled with [3H]AVP and p[NH]ppG, suggesting that this receptor complex had dissociated during chromatography. It is possible therefore that the high-Mr complex contains the hormone, its receptor and a guanine nucleotide binding protein.
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002850:Chromatography, Gel; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D046911:Macromolecular Substances; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000187:drug effects*; D017483:Receptors, Vasopressin
D046911:Macromolecular Substances; D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins