Conformational changes in the G protein Gs induced by the β2 adrenergic receptor

Nature. 2011 Sep 28;477(7366):611-5. doi: 10.1038/nature10488.

Abstract

G protein-coupled receptors represent the largest family of membrane receptors that instigate signalling through nucleotide exchange on heterotrimeric G proteins. Nucleotide exchange, or more precisely, GDP dissociation from the G protein α-subunit, is the key step towards G protein activation and initiation of downstream signalling cascades. Despite a wealth of biochemical and biophysical studies on inactive and active conformations of several heterotrimeric G proteins, the molecular underpinnings of G protein activation remain elusive. To characterize this mechanism, we applied peptide amide hydrogen-deuterium exchange mass spectrometry to probe changes in the structure of the heterotrimeric bovine G protein, Gs (the stimulatory G protein for adenylyl cyclase) on formation of a complex with agonist-bound human β(2) adrenergic receptor (β(2)AR). Here we report structural links between the receptor-binding surface and the nucleotide-binding pocket of Gs that undergo higher levels of hydrogen-deuterium exchange than would be predicted from the crystal structure of the β(2)AR-Gs complex. Together with X-ray crystallographic and electron microscopic data of the β(2)AR-Gs complex (from refs 2, 3), we provide a rationale for a mechanism of nucleotide exchange, whereby the receptor perturbs the structure of the amino-terminal region of the α-subunit of Gs and consequently alters the 'P-loop' that binds the β-phosphate in GDP. As with the Ras family of small-molecular-weight G proteins, P-loop stabilization and β-phosphate coordination are key determinants of GDP (and GTP) binding affinity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-2 Receptor Agonists / chemistry
  • Adrenergic beta-2 Receptor Agonists / metabolism
  • Animals
  • Biocatalysis
  • Catalytic Domain
  • Cattle
  • Crystallography, X-Ray
  • Deuterium Exchange Measurement
  • GTP-Binding Protein alpha Subunits, Gs / chemistry*
  • GTP-Binding Protein alpha Subunits, Gs / metabolism*
  • GTP-Binding Protein alpha Subunits, Gs / ultrastructure
  • Guanosine Diphosphate / metabolism
  • Guanosine Triphosphate / metabolism
  • Humans
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Receptors, Adrenergic, beta-2 / chemistry*
  • Receptors, Adrenergic, beta-2 / metabolism*
  • Receptors, Adrenergic, beta-2 / ultrastructure

Substances

  • Adrenergic beta-2 Receptor Agonists
  • Receptors, Adrenergic, beta-2
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • GTP-Binding Protein alpha Subunits, Gs

Grant support