title: A GPR-protein interaction surface of Gi(alpha): implications for the mechanism of GDP-release inhibition.
abstract: Proteins containing G-protein regulatory (GPR) motifs represent a novel family of guanine nucleotide dissociation inhibitors (GDIs) for G(alpha) subunits from the Gi family. They selectively interact with the GDP-bound conformation of Gi(alpha) and transducin-alpha (Gt(alpha)), but not with Gs(alpha). A series of chimeric proteins between Gi(alpha)(1) and Gs(alpha) has been constructed to investigate GPR-contact sites on G(alpha) subunits and the mechanism of GPR-protein GDI activity. Analysis of the interaction of two GPR-proteins-AGS3GPR and Pcp2-with the chimeric G(alpha) subunits demonstrated that the GPR-Gi(alpha)(1) interface involves the Gi(alpha)(1) switch regions and Gi(alpha)(1)-144-151, a site within the helical domain. Residues within Gi(alpha)(1)-144-151 form conformation-sensitive contacts with switch III, and may directly interact with a GPR-protein or form a GPR-binding surface jointly with switch III. The helical domain site is critical to the ability of GPR-proteins to act as GDIs. Our data suggest that a mechanism of the GDI activity of GPR-proteins is different from that of GDIs for monomeric GTPases and from the GDI-like activity of G(betagamma) subunits. The GPR-proteins are likely to block a GDP-escape route on G(alpha) subunits.
authors.affiliation: Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Natochin
authors.forename: Karim G
authors.initials: KG
authors.lastname: Gasimov
authors.forename: Nikolai O
authors.initials: NO
authors.lastname: Artemyev
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D002678:Chimera; D003001:Cloning, Molecular; D020555:GTP-Binding Protein Regulators / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D051381:Rats; D014357:Trypsin / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D020555:GTP-Binding Protein Regulators; C498913:Gpsm1 protein, rat; D020662:Guanine Nucleotide Exchange Factors; D009479:Neuropeptides; C104971:Pcp2 protein, mouse; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D014357:Trypsin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go