Structural basis of G protein-coupled receptor-G protein interactions.
The interaction of G protein-coupled receptors (GPCRs) with heterotrimeric G proteins represents one of the most fundamental biological processes. However, the molecular architecture of the GPCR-G protein complex remains poorly defined. In the present study, we applied a comprehensive GPCR-G protein alpha subunit (Galpha) chemical cross-linking strategy to map a receptor-Galpha interface, both before and after agonist-induced receptor activation. Using the M(3) muscarinic acetylcholine receptor (M3R)-Galpha(q) system as a model system, we examined the ability of approximately 250 combinations of cysteine-substituted M3R and Galpha(q) proteins to undergo cross-link formation. We identified many specific M3R-Galpha(q) contact sites, in both the inactive and active receptor conformations, allowing us to draw conclusions regarding the basic architecture of the M3R-Galpha(q) interface and the nature of the conformational changes following receptor activation. As heterotrimeric G proteins as well as most GPCRs share a high degree of structural homology, our findings should be of broad general relevance.
Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA. jianxinh@niddk.nih.gov
Jianxin
J
Hu
Yan
Y
Wang
Xiaohong
X
Zhang
John R
JR
Lloyd
Jian Hua
JH
Li
Joel
J
Karpiak
Stefano
S
Costanzi
Jürgen
J
Wess
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D044385:GTP-Binding Protein alpha Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D011976:Receptors, Muscarinic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D044385:GTP-Binding Protein alpha Subunits; D011976:Receptors, Muscarinic