G protein antagonists. A novel hydrophobic peptide competes with receptor for G protein binding

J Biol Chem. 1992 Aug 15;267(23):16237-43.

Abstract

A substance P (SP) analog, [D-Pro4,D-Trp7,9,10] SP4-11, is known to inhibit the actions of various structurally unrelated messenger molecules as well as SP. Our studies on the effects of this peptide on the regulation of purified G proteins by receptor showed that at least some of the biological effects of the peptide can be explained by the ability of the peptide to block the activation of G proteins by receptors. Here we report that a novel truncated SP-related peptide, pGlu-Gln-D-Trp-Phe-D-Trp-D-Trp-Met-NH2, inhibited the activation of G(i) or G(o) by M2 muscarinic cholinergic receptor (M2 mAChR) or of Gs by beta-adrenergic receptor in the reconstituted phospholipid vesicles, assayed by receptor-promoted GTP hydrolysis. The inhibition by the peptide was apparently reversible and competitive with respect to receptor binding to G proteins; the inhibition could be overcome by increasing the concentration of receptor in the vesicles and was not altered by changes in the concentration of G protein. The competing effects of the peptide were used to analyze the effect of agonist on receptor-G protein interaction. The concentration change of muscarinic agonist did not alter the inhibitory effects of the peptide on M2 mAChR-promoted GTPase by G(o), which is consistent with the idea that agonist increases the regulatory efficiency of the receptor but does not alter its affinity for G proteins. This new group of compounds (G protein antagonists) is a promising tool to study receptor-G protein interaction quantitatively.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding, Competitive
  • Brain / metabolism
  • Carbachol / pharmacology
  • Cattle
  • Cell Line
  • GTP-Binding Proteins / antagonists & inhibitors
  • GTP-Binding Proteins / isolation & purification
  • GTP-Binding Proteins / metabolism*
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Guanosine Triphosphate / metabolism
  • Humans
  • Insecta
  • Kinetics
  • Macromolecular Substances
  • Molecular Sequence Data
  • Oligopeptides / chemical synthesis
  • Oligopeptides / pharmacology
  • Peptide Fragments*
  • Receptors, Adrenergic, beta / drug effects
  • Receptors, Adrenergic, beta / metabolism*
  • Receptors, Muscarinic / drug effects
  • Receptors, Muscarinic / metabolism*
  • Structure-Activity Relationship
  • Substance P / analogs & derivatives*
  • Substance P / pharmacology*
  • Transfection
  • Turkeys

Substances

  • Macromolecular Substances
  • Oligopeptides
  • Peptide Fragments
  • Receptors, Adrenergic, beta
  • Receptors, Muscarinic
  • Substance P
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • substance P (4-11), Pro(4)-Trp(7,9,10)-
  • Guanosine Triphosphate
  • Carbachol
  • GTP-Binding Proteins