Abstract
The activation of G proteins by G protein-coupled receptors (GPCRs) underlies the majority of transmembrane signaling by hormones and neurotransmitters. Recent structures of GPCR-G protein complexes obtained by crystallography and cryoelectron microscopy (cryo-EM) reveal similar interactions between GPCRs and the alpha subunit of different G protein isoforms. While some G protein subtype-specific differences are observed, there is no clear structural explanation for G protein subtype-selectivity. All of these complexes are stabilized in the nucleotide-free state, a condition that does not exist in living cells. In an effort to better understand the structural basis of coupling specificity, we used time-resolved structural mass spectrometry techniques to investigate GPCR-G protein complex formation and G-protein activation. Our results suggest that coupling specificity is determined by one or more transient intermediate states that serve as selectivity filters and precede the formation of the stable nucleotide-free GPCR-G protein complexes observed in crystal and cryo-EM structures. A time-resolved look at how a GPCR engages a G protein reveals intermediates in the process that dictate both specificity for the interaction and the initial steps kicking off downstream signaling.
Original language | English |
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Pages (from-to) | 1232-1242 |
Number of pages | 11 |
Journal | Cell |
Volume | 177 |
Issue number | 5 |
DOIs | |
Publication status | Published - 16 May 2019 |
Externally published | Yes |
Keywords
- conformation
- dynamics
- G protein
- G protein-coupled receptor
- hydrogen/deuterium exchange mass spectrometry
- hydroxyl radical footprinting mass spectrometry