Three Forms of Gi Discriminated by Synthetic Peptide Antisera

  • Susanne M. Mumby


Two signal transduction pathways that are regulated by guanine nucleotide-binding proteins (G proteins) have been well characterized: the light-stimulated visual cascade and the hormone-sensitive adenylyl cyclase system (for review see Stryer, 1986; Gilman, 1987). Stimulation of retinal cyclic GMP phosphodiesterase by the photoreceptor rhodopsin is mediated by the G protein Gt (also referred to as transducin). Hormone-sensitive adenylyl cyclase is under dual stimulatory and inhibitory control by two other G proteins, Gs and Gi Receptors that stimulate adenylyl cyclase are coupled to the enzyme by Gg, whereas inhibitory receptors are coupled by Gi. These classical G proteins exhibit a characteristic heterotrimeric subunit structure. The ß and γ subunits are tightly associated with each other and in some cases are functionally interchangeable between different α subunits. The α subunits display more structural heterogeneity and functional specificity, and thus they serve to distinguish the different G protein oligomers. The α subunits possess a high-affinity binding site for guanine nucleotides and an intrinsic GTPase activity that are involved in the activation and deactivation of the G protein. Toxins from Vibrio cholerae and Bordetella pertussis are capable of covalently modifying and functionally altering a subunits. Cholera toxin catalyzes the ADP-ribosylation of Gs and Gt. ADP-ribosylation by pertussis toxin blocks activation of Gt and Gi by receptors. Activation of G proteins in detergent solution (and Gt in phospholipid vesicles) by nonhydrolyzable analogs of GTP involves dissociation of the α subunit from βγ. It is the α subunits of Gs and Gts and αt) that stimulate their respective effector enzymes.


Adenylyl Cyclase Guanine Nucleotide Pertussis Toxin Bovine Brain Rabbit Liver 
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  1. Bokoch, G. M., T. Katada, J. K. Northup, M. Ui, and A. Gilman, Purification and properties of the inhibitory guanine nucleotide-binding regulatory component of adenylate cyclase, J. Biol. Chem. 259:3560–3567 (1984).PubMedGoogle Scholar
  2. Bray, P., A. Carter, V. Guo, C. Puckett, J. Kamholz, A. Spiegel, and M. Nirenberg, Human cDNA clones for an α subunit of Gi signal-transduction protein, Proc. Natl. Acad. Sci. USA 84:5115–5119 (1987).PubMedCrossRefGoogle Scholar
  3. Burch, R. M., A. Luini, and J. Axelrod, Phospholipase A2 and phospholipase C are activated by distinct GTP-binding proteins in response to at-adrenergic stimulation in FRTL5 thyroid cells, Proc. Natl. Acad. Sci. USA 83: 7201–7205 (1986).PubMedCrossRefGoogle Scholar
  4. Carty, D. J., S. M. Mumby, E. Padrell, J. Codina, R. Graf, L. Birnbaumer, A. G. Gilman, and R. Iyengar, The GTP-binding regulatory proteins of human erythrocytes: Evidence for three distinct pertussis toxin substrates in the 40–41 kDalton range. Submitted for publication.Google Scholar
  5. Cerbai, E., U. Klockner, and G. Isenberg, The a subunit of the GTP-binding protein activates muscarinic potassium channels of the atrium, Science 240:1782–1783 (1988).PubMedCrossRefGoogle Scholar
  6. Cockcroft, S. 1987. Polyphosphoinositide phosphodiesterase: regulation by a novel guanine nucleotide binding protein, Gp, Trends Biochem. Sci. 12:75–78 (1987).CrossRefGoogle Scholar
  7. Codina, J., J. Olate, J. Abramowitz, R. Mattera, R. G. Cook, and L. Birnbaumer, αi-3 cDNA encodes the α subunit of Gk, the stimulatory G protein of receptor-regulated K+ channels, J. Biol. Chem. 263:6746–6750 (1988).PubMedGoogle Scholar
  8. Didsbury, J. R., Y. Ho, and R. Snyderman, Human G- protein a-subunit: deduction of amino acid structure from a cloned cDNA, FEBS Lett. 211:160–164 (1987).PubMedCrossRefGoogle Scholar
  9. Didsbury, J. R., and R. Snyderman, Molecular cloning of a new human G protein; evidence for two G-like protein families, FEBS Lett. 219:259–263 (1987).PubMedCrossRefGoogle Scholar
  10. Ewald, D. A., P. C. Sternweis, and R. J. Miller, G induced coupling of NPY receptors to calcium channels in sensory neurons, Proc. Natl. Acad. Sci. USA In press. (1988)Google Scholar
  11. Florio, V. A., and P. C. Sternweis, Reconstitution of resolved muscarinic cholinergic receptors with purified GTP-binding proteins, J. Biol. Chem. 260:3477–3483 (1985).PubMedGoogle Scholar
  12. Goldsmith, P., P. Gierschik, G. Milligan, C. G. Unson, R. Vinitisky, H. L. Malech, and A. Spiegal, Antibodies directed against synthetic peptides distinguish between GTP- binding proteins in neutrophil and brain, J. Biol. Chem. 262:14683–14688 (1987).PubMedGoogle Scholar
  13. Gilman, A. G., G proteins: transducers of receptor-generated signals, Ann. Rev. Biochem. 56:615–649 (1987).PubMedCrossRefGoogle Scholar
  14. Graziano, M. P., P. J. Casey, and A. G. Gilman, Expression of cDNAs for G proteins in Escherichia coli: two forms of G stimulate adenylyl cyclase, J. Biol. Chem. 262:11375–11381 (1987).PubMedGoogle Scholar
  15. Graziano, M. P., M. Freissmuth, and A. G. Gilman, Expression of G in Escherichia coli: Purification and properties of two forms of the protein, J. Biol. Chem. In press.Google Scholar
  16. Hescheler, J., W. Rosenthal, W. Trautwein, and G. Schultz, The GTP-binding protein, GO, regulates neuronal calcium channels, Nature 325:445–447 (1987).PubMedCrossRefGoogle Scholar
  17. Itoh, H., T. Kozasa, S. Nagata, S. Nakamura, T. Katada, M. Ui, S. Iwai, E. Ohtsuka, H. Kawasaki, K. Suzuki, and Y. Kaziro, Molecular cloning and sequence determination of cDNAs for α subunits of the guanine nucleotide-binding proteins Gs, Gi, and GO from rat brain, Proc. Natl. Acad. Sci. USA 83:3776–3780 (1986).PubMedCrossRefGoogle Scholar
  18. Itoh, H., R. Toyama, T. Kozasa, T. Tusukamoto, M. Matsomka, and Y. Kaziro, Presence of three distinct molecular species of Gi protein a subunit, J. Biol. Chem. 263:6656–6664 (1988).PubMedGoogle Scholar
  19. Katada, T., G. M. Bokoch, M. D. Smigel, M. Ui, and A. G. Gilman, The inhibitory guanine nucleotide-binding regulatory component of adenylate cyclase. Subunit dissociation and the inhibition of adenylate cyclase in S49 lymphoma cyc- and wild type membranes, J. Biol. Chem. 259:3586–3595 (1984).PubMedGoogle Scholar
  20. Katada, T., J. K. Northup, G. M. Bokoch, M. Ui, and A. G. Gilman, The inhibitory guanine nucleotide-binding regulatory component of adenylate cyclase. Subunit dissociation and guanine nucleotide-dependent hormonal inhibition. J. Biol. Chem., 259:3578–3585 (1984).PubMedGoogle Scholar
  21. Katada, T., M. Oinuma, K. Kusakabe, and M. Ui, A new GTP-binding protein in brain tissues serving as the specific substrate of islet-activating protein, pertussis toxin, FEBS Lett. 213:353–358 (1987).PubMedCrossRefGoogle Scholar
  22. Logothetis, D. E., Y. Kurachi, J. Galper, E. J. Neer, and D. E. Clapham, The ßγ subunits of GTP-binding proteins activate the muscarinic K+ channel in heart, Nature 325:321–326 (1987).PubMedCrossRefGoogle Scholar
  23. Mumby, S. M., I. Pang, A. G. Gilman, and P. C. Sternweis, Chromatographic resolution and immunologic identification of the α40 and α41 subunits of guanine nucleotide-binding regulatory proteins from bovine brain, J. Biol. Chem. 263:2020–2026 (1988).PubMedGoogle Scholar
  24. Mumby, S. M., R. A. Kahn, D. R. Manning, and A. G. Gilman, Antisera of designed specificity for subunits of guanine nucleotide-binding regulatory proteins. Proc. Natl. Acad. Sci. USA 83:265–269 (1986).PubMedCrossRefGoogle Scholar
  25. Nukada, T., T. Tanabe, H. Takahashi, M. Noda, K. Haga, T. Haga, A. Ichiyama, K. Kangawa, M. Hiranaga, H. Matsuo, and S. Numa, Primary structure of the α-subunit of bovine adenylate cyclase-inhibiting G-protein deduced from the cDNA sequence, FEBS Lett. 197:305–310 (1986).PubMedCrossRefGoogle Scholar
  26. Sternweis, P. C., and J. D. Robishaw, Isolation of two proteins with high affinity for guanine nucleotides from membranes of bovine brain, J. Biol. Chem. 259:13806–13813 (1984).PubMedGoogle Scholar
  27. Stryer, L., Cyclic GMP cascade of vision, Ann. Rev. Neurosci. 9:87–119 (1986).PubMedCrossRefGoogle Scholar
  28. Suki, W. N., J. Abramowitz, R. Mattera, J. Codina, and L. Birnbaumer, The human genome encodes at least three non-allellic G proteins with a—type subunits, FEBS Lett. 220:187–192 (1987).PubMedCrossRefGoogle Scholar
  29. Sullivan, K. A., Y. Liao, A. Alborzi, B. Biederman, F. Chang, S. B. Masters, A. D. Levinson, and H. R. Bourne, Inhibitory and stimulatory G proteins of adenylate cyclase: cDNA and amino acid sequences of the α chains, Proc. Natl. Acad. Sci. U.S.A. 83:6687–6691 (1986).PubMedCrossRefGoogle Scholar
  30. Yatani, A., J. Codina, A. M. Brown, and L. Birnbaumer, Direct activation of mammalian atrial muscarinic potassium channel by GTP regulatory protein GK, Science 235:207–211 (1987).PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1989

Authors and Affiliations

  • Susanne M. Mumby
    • 1
  1. 1.Department of PharmacologyUniversity of Texas Southwestern Medical Center at DallasDallasUSA

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