Structural highlights
Function
[GNAI1_HUMAN] Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. The G(i) proteins are involved in hormonal regulation of adenylate cyclase: they inhibit the cyclase in response to beta-adrenergic stimuli. The inactive GDP-bound form prevents the association of RGS14 with centrosomes and is required for the translocation of RGS14 from the cytoplasm to the plasma membrane. May play a role in cell division.[1] [2] [GBG2_BOVIN] Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction. [GBB1_RAT] Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction.
Publication Abstract from PubMed
AIM: Dominant negative mutant G proteins have provided critical insight into the mechanisms of G protein-coupled receptor (GPCR) signaling, but the mechanisms underlying the dominant negative characteristics are not completely understood. The aim of this study was to determine the structure of the dominant negative Galphai1beta1gamma2 G203A/A326S complex (Gi-DN) and to reveal the structural basis of the mutation-induced phenotype of Galphai1beta1gamma2. METHODS: The three subunits of the Gi-DN complex were co-expressed with a baculovirus expression system. The Gi-DN heterotrimer was purified, and the structure of its complex with GDP was determined through X-ray crystallography. RESULTS: The Gi-DN heterotrimer structure revealed a dual mechanism underlying the dominant negative characteristics. The mutations weakened the hydrogen bonding network between GDP/GTP and the binding pocket residues, and increased the interactions in the Galpha-Gbetagamma interface. Concomitantly, the Gi-DN heterotrimer adopted a conformation, in which the C-terminus of Galphai and the N-termini of both the Gbeta and Ggamma subunits were more similar to the GPCR-bound state compared with the wild type complex. From these structural observations, two additional mutations (T48F and D272F) were designed that completely abolish the GDP binding of the Gi-DN heterotrimer. CONCLUSION: Overall, the results suggest that the mutations impede guanine nucleotide binding and Galpha-Gbetagamma protein dissociation and favor the formation of the G protein/GPCR complex, thus blocking signal propagation. In addition, the structure provides a rationale for the design of other mutations that cause dominant negative effects in the G protein, as exemplified by the T48F and D272F mutations.
The structural basis of the dominant negative phenotype of the Galphai1beta1gamma2 G203A/A326S heterotrimer.,Liu P, Jia MZ, Zhou XE, De Waal PW, Dickson BM, Liu B, Hou L, Yin YT, Kang YY, Shi Y, Melcher K, Xu HE, Jiang Y Acta Pharmacol Sin. 2016 Sep;37(9):1259-72. doi: 10.1038/aps.2016.69. Epub 2016, Aug 8. PMID:27498775[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Cho H, Kehrl JH. Localization of Gi alpha proteins in the centrosomes and at the midbody: implication for their role in cell division. J Cell Biol. 2007 Jul 16;178(2):245-55. PMID:17635935 doi:10.1083/jcb.200604114
- ↑ Johnston CA, Siderovski DP. Structural basis for nucleotide exchange on G alpha i subunits and receptor coupling specificity. Proc Natl Acad Sci U S A. 2007 Feb 6;104(6):2001-6. Epub 2007 Jan 30. PMID:17264214
- ↑ Liu P, Jia MZ, Zhou XE, De Waal PW, Dickson BM, Liu B, Hou L, Yin YT, Kang YY, Shi Y, Melcher K, Xu HE, Jiang Y. The structural basis of the dominant negative phenotype of the Galphai1beta1gamma2 G203A/A326S heterotrimer. Acta Pharmacol Sin. 2016 Sep;37(9):1259-72. doi: 10.1038/aps.2016.69. Epub 2016, Aug 8. PMID:27498775 doi:http://dx.doi.org/10.1038/aps.2016.69
