title: Disruption of receptor-mediated activation of G protein by mutating a conserved arginine residue in the switch II region of the alpha subunit.
abstract: A naturally occurring point mutation (R231H) within one of the major 3gamma-binding surface (switch II region) on the a subunit of Gs (alpha(s)) has previously been found to disrupt receptor-mediated activation of Gs. The disruption caused by mutating this conserved residue may be a general phenomenon for all a subunits. Homologous mutants of the alpha subunit of Gz [alpha(z); a negative regulator of adenylyl cyclase (AC)] and G16 (alpha16; a stimulator of phospholipase C) were constructed and examined for receptor-mediated regulation of their corresponding effectors. The mutant alphazR209H cannot be fully activated by the delta-opioid receptor, as indicated by the impairment of the inhibition of alpha(s)-stimulated AC and betagamma-mediated stimulation of AC type II (AC2). Similarly, the mutant alpha16R216H lost the ability to mediate receptor-induced activation of phospholipase C and AC2. The receptor coupling efficacy and promiscuity of alpha16R216H were eradicated. The mutation of the conserved arginine has no observable effect on the constitutive activities of the GTPase-deficient derivatives of both alpha(z) and alpha16. The alpha subunit of Gt1 (transducin; alphat1) attenuated betagamma-mediated stimulation of AC2 by sequestrating free betagamma subunits, but the mutant alphat1R204H showed reduced ability to scavenge betagamma-mediated AC2 activation. Presumably, mutation of the conserved arginine disrupted the subunit interactions in addition to the impairment of receptor interaction.
authors.affiliation: Department of Biology and Biotechnology Research Institute, Hong Kong University of Science and Technology, Kowloon, China.
authors.forename: M K
authors.initials: MK
authors.lastname: Ho
authors.forename: L Y
authors.initials: LY
authors.lastname: Yung
authors.forename: Y H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000235:genetics*; D019556:COS Cells; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011487:Protein Conformation; D017447:Receptors, Dopamine D1 / Q000502:physiology; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000502:physiology; D017465:Receptors, Opioid, delta / Q000502:physiology*; D018000:Receptors, Peptide / Q000502:physiology; D018047:Receptors, Purinergic P1 / Q000502:physiology; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D007295:Inositol Phosphates; D017447:Receptors, Dopamine D1; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D017465:Receptors, Opioid, delta; D018000:Receptors, Peptide; D018047:Receptors, Purinergic P1; D001120:Arginine; D010738:Type C Phospholipases; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases