title: Stabilization of the GDP-bound conformation of Gialpha by a peptide derived from the G-protein regulatory motif of AGS3.
abstract: The G-protein regulatory (GPR) motif in AGS3 was recently identified as a region for protein binding to heterotrimeric G-protein alpha subunits. To define the properties of this approximately 20-amino acid motif, we designed a GPR consensus peptide and determined its influence on the activation state of G-protein and receptor coupling to G-protein. The GPR peptide sequence (28 amino acids) encompassed the consensus sequence defined by the four GPR motifs conserved in the family of AGS3 proteins. The GPR consensus peptide effectively prevented the binding of AGS3 to Gialpha1,2 in protein interaction assays, inhibited guanosine 5'-O-(3-thiotriphosphate) binding to Gialpha, and stabilized the GDP-bound conformation of Gialpha. The GPR peptide had little effect on nucleotide binding to Goalpha and brain G-protein indicating selective regulation of Gialpha. Thus, the GPR peptide functions as a guanine nucleotide dissociation inhibitor for Gialpha. The GPR consensus peptide also blocked receptor coupling to Gialphabetagamma indicating that although the AGS3-GPR peptide stabilized the GDP-bound conformation of Gialpha, this conformation of Gialpha(GDP) was not recognized by a G-protein coupled receptor. The AGS3-GPR motif presents an opportunity for selective control of Gialpha- and Gbetagamma-regulated effector systems, and the GPR motif allows for alternative modes of signal input to G-protein signaling systems.
authors.affiliation: Departments of Pharmacology and Library and Informatics, Medical University of South Carolina, Charleston, South Carolina 29403, USA.
authors.forename: Y K
authors.initials: YK
authors.lastname: Peterson
authors.forename: M L
authors.initials: ML
authors.lastname: Bernard
authors.forename: H
authors.initials: H
authors.lastname: Ma
authors.forename: S
authors.initials: S
authors.lastname: Hazard
authors.forename: S G
authors.initials: SG
authors.lastname: Graber
authors.forename: S M
authors.initials: SM
authors.lastname: Lanier
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D020555:GTP-Binding Protein Regulators / Q000737:chemistry*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D018411:Spodoptera; D013329:Structure-Activity Relationship
chemical_list: D020555:GTP-Binding Protein Regulators; D006153:Guanosine Diphosphate; D019206:GTP-Binding Protein alpha Subunits, Gi-Go