title: Guanine nucleotide regulation of B2 kinin receptors. Time-dependent formation of a guanine nucleotide-sensitive receptor state from which [3H]bradykinin dissociates slowly.
abstract: We have examined the binding of [3H]bradykinin to bovine myometrial membranes and assessed its sensitivity to guanine nucleotides. Total binding displayed a typical B2 kinin receptor specificity. However, saturation binding isotherms were resolved into at least two components with KD values of 8 pM (45%) and 378 pM (55%). Low affinity binding exhibited relatively rapid rates of association (kobs = 1.40 x 10(-2) s-1) and dissociation (k-1 = 3.82 x 10(-3) s-1), while high affinity binding exhibited considerably slower rates (kobs = 9.52 x 10(-4) s-1 and k-1 = 4.43 x 10(-5) s-1). Pre-equilibrium dissociation kinetics revealed that formation of high affinity binding was characterized as a time-dependent accumulation of the slow dissociation rate at the expense of at least one other more rapid dissociation rate. In the presence of 10 microM guanyl-5'-yl imidodiphosphate (Gpp(NH)p), at least two binding components were resolved with KD values of 37 pM (12%) and 444 pM (88%). Gpp(NH)p apparently specifically perturbed high affinity binding by completely preventing the accumulation of the slow dissociation phase. Instead, two more rapid dissociation rates (k-1 = 8.53 x 10(-3) s-1 and 4.43 x 10(-4) s-1) were observed. These results suggest that [3H]bradykinin interacts with at least two B2 kinin receptor-like binding sites in bovine myometrial membranes. A three-state model for the guanine nucleotide-sensitive agonist interaction with the high affinity binding sites is proposed.
authors.affiliation: Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
authors.forename: L M
authors.initials: LM
authors.lastname: Leeb-Lundberg
authors.forename: S A
authors.initials: SA
authors.lastname: Mathis
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D009215:Myometrium / Q000378:metabolism*; D011869:Radioligand Assay; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
chemical_list: D006150:Guanine Nucleotides; D018002:Receptors, Bradykinin; D017981:Receptors, Neurotransmitter; D000266:Adenylyl Imidodiphosphate; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D001920:Bradykinin