5tdh

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.