A universal allosteric mechanism for G protein activation.
G proteins play a central role in signal transduction and pharmacology. Signaling is initiated by cell-surface receptors, which promote guanosine triphosphate (GTP) binding and dissociation of Gα from the Gβγ subunits. Structural studies have revealed the molecular basis of subunit association with receptors, RGS proteins, and downstream effectors. In contrast, the mechanism of subunit dissociation is poorly understood. We use cell signaling assays, molecular dynamics (MD) simulations, and biochemistry and structural analyses to identify a conserved network of amino acids that dictates subunit release. In the presence of the terminal phosphate of GTP, a glycine forms a polar network with an arginine and glutamate, putting torsional strain on the subunit binding interface. This "G-R-E motif" secures GTP and, through an allosteric link, discharges the Gβγ dimer. Replacement of network residues prevents subunit dissociation regardless of agonist or GTP binding. These findings reveal the molecular basis of the final committed step of G protein activation.
['Knight|Kevin M|KM|', 'Ghosh|Soumadwip|S|', 'Campbell|Sharon L|SL|', 'Lefevre|Tyler J|TJ|', 'Olsen|Reid H J|RHJ|', 'Smrcka|Alan V|AV|', 'Valentin|Natalie H|NH|', 'Yin|Guowei|G|', 'Vaidehi|Nagarajan|N|', 'Dohlman|Henrik G|HG|']
D000494:Allosteric Regulation D020816:Amino Acid Motifs D006160:Guanosine Triphosphate D057809:HEK293 Cells D020962:Heterotrimeric GTP-Binding Proteins D006801:Humans D056004:Molecular Dynamics Simulation D012441:Saccharomyces cerevisiae D029701:Saccharomyces cerevisiae Proteins
G protein biolayer interferometry bioluminescence resonance energy transfer human molecular dynamics simulation nuclear magnetic resonance spectroscopy protein allostery protein thermostability x-ray crystal structure yeast