title: Backbone resonance assignments for G protein α(i3) subunit in the GDP-bound state.
abstract: Guanine-nucleotide binding proteins (G proteins) serve as molecular switches in signaling pathways, by coupling the activation of G protein-coupled receptors (GPCRs) at the cell surface to intracellular responses. In the resting state, G protein forms a heterotrimer, consisting of the G protein α subunit with GDP (Gα·GDP) and the G protein βγ subunit (Gβγ). Ligand binding to GPCRs promotes the GDP-GTP exchange on Gα, leading to the dissociation of the GTP-bound form of Gα (Gα·GTP) and Gβγ. Then, Gα·GTP and Gβγ bind to their downstream effector enzymes or ion channels and regulate their activities, leading to a variety of cellular responses. Finally, Gα hydrolyzes the bound GTP to GDP and returns to the resting state by re-associating with Gβγ. The G proteins are classified with four major families based on the amino acid sequences of Gα: i/o, s, q/11, and 12/13. Here, we established the backbone resonance assignments of human Gαi3, a member of the i/o family with a molecular weight of 41 K, in complex with GDP. The chemical shifts were compared with those of Gα(i3) in complex with a GTP-analogue, GTPγS, which we recently reported, indicating that the residues with significant chemical shift differences are mostly consistent with the regions with the structural differences between the GDP- and GTPγS-bound states, as indicated in the crystal structures. The assignments of Gα(i3)·GDP would be useful for the analyses of the dynamics of Gα(i3) and its interactions with various target molecules.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mase
authors.forename: Mariko
authors.initials: M
authors.lastname: Yokogawa
authors.forename: Masanori
authors.initials: M
authors.lastname: Osawa
authors.forename: Ichio
authors.initials: I
authors.lastname: Shimada
mesh_terms: D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry* / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000737:chemistry / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019206:GTP-Binding Protein alpha Subunits, Gi-Go