Structural basis for allosteric regulation of GPCRs by sodium ions.
Pharmacological responses of G protein-coupled receptors (GPCRs) can be fine-tuned by allosteric modulators. Structural studies of such effects have been limited due to the medium resolution of GPCR structures. We reengineered the human A(2A) adenosine receptor by replacing its third intracellular loop with apocytochrome b(562)RIL and solved the structure at 1.8 angstrom resolution. The high-resolution structure allowed us to identify 57 ordered water molecules inside the receptor comprising three major clusters. The central cluster harbors a putative sodium ion bound to the highly conserved aspartate residue Asp(2.50). Additionally, two cholesterols stabilize the conformation of helix VI, and one of 23 ordered lipids intercalates inside the ligand-binding pocket. These high-resolution details shed light on the potential role of structured water molecules, sodium ions, and lipids/cholesterol in GPCR stabilization and function.
Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Wei
W
Liu
Eugene
E
Chun
Aaron A
AA
Thompson
Pavel
P
Chubukov
Fei
F
Xu
Vsevolod
V
Katritch
Gye Won
GW
Han
Christopher B
CB
Roth
Laura H
LH
Heitman
Adriaan P
AP
IJzerman
Vadim
V
Cherezov
Raymond C
RC
Stevens
D058908:Adenosine A2 Receptor Agonists / Q000378:metabolism; D058917:Adenosine A2 Receptor Antagonists / Q000378:metabolism; D000494:Allosteric Regulation; D002784:Cholesterol / Q000737:chemistry; D018360:Crystallography, X-Ray; D003573:Cytochrome b Group / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D006860:Hydrogen Bonding; D008024:Ligands; D008051:Lipid Bilayers; D008055:Lipids / Q000737:chemistry; D008958:Models, Molecular; D011487:Protein Conformation; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D043705:Receptor, Adenosine A2A / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012964:Sodium / Q000032:analysis*; D014227:Triazines / Q000378:metabolism; D014230:Triazoles / Q000378:metabolism; D014867:Water / Q000737:chemistry
D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; D008024:Ligands; D008051:Lipid Bilayers; D008055:Lipids; D043705:Receptor, Adenosine A2A; D011993:Recombinant Fusion Proteins; D014227:Triazines; D014230:Triazoles; C097270:ZM 241385; D014867:Water; C017850:cytochrome b562, E coli; D002784:Cholesterol; D012964:Sodium