title: Structure of the human angiotensin II type 1 (AT1) receptor bound to angiotensin II from multiple chemoselective photoprobe contacts reveals a unique peptide binding mode.
abstract: Breakthroughs in G protein-coupled receptor structure determination based on crystallography have been mainly obtained from receptors occupied in their transmembrane domain core by low molecular weight ligands, and we have only recently begun to elucidate how the extracellular surface of G protein-coupled receptors (GPCRs) allows for the binding of larger peptide molecules. In the present study, we used a unique chemoselective photoaffinity labeling strategy, the methionine proximity assay, to directly identify at physiological conditions a total of 38 discrete ligand/receptor contact residues that form the extracellular peptide-binding site of an activated GPCR, the angiotensin II type 1 receptor. This experimental data set was used in homology modeling to guide the positioning of the angiotensin II (AngII) peptide within several GPCR crystal structure templates. We found that the CXC chemokine receptor type 4 accommodated the results better than the other templates evaluated; ligand/receptor contact residues were spatially grouped into defined interaction clusters with AngII. In the resulting receptor structure, a β-hairpin fold in extracellular loop 2 in conjunction with two extracellular disulfide bridges appeared to open and shape the entrance of the ligand-binding site. The bound AngII adopted a somewhat vertical binding mode, allowing concomitant contacts across the extracellular surface and deep within the transmembrane domain core of the receptor. We propose that such a dualistic nature of GPCR interaction could be well suited for diffusible linear peptide ligands and a common feature of other peptidergic class A GPCRs.
authors: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors: Dany
authors: D
authors: Fillion
authors: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors: Jérôme
authors: J
authors: Cabana
authors: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors: Gaétan
authors: G
authors: Guillemette
authors: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors: Richard
authors: R
authors: Leduc
authors: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors: Pierre
authors: P
authors: Lavigne
authors: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada. Electronic address: Emanuel.Escher@USherbrooke.ca.
authors: Emanuel
authors: E
authors: Escher
mesh_terms: D000345:Affinity Labels / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000737:chemistry*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D008715:Methionine / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D015335:Molecular Probes / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D055668:Photochemical Processes; D011485:Protein Binding; D017433:Protein Structure, Secondary; D044140:Receptor, Angiotensin, Type 1 / Q000737:chemistry* / Q000235:genetics; D040681:Structural Homology, Protein
chemical_list: D000345:Affinity Labels; D015335:Molecular Probes; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D008715:Methionine
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