Crystal structure of glucagon-like peptide-1 in complex with the extracellular domain of the glucagon-like peptide-1 receptor.
GLP-1 (glucagon-like peptide-1) is an incretin released from intestinal L-cells in response to food intake. Activation of the GLP-1 receptor potentiates the synthesis and release of insulin from pancreatic beta-cells in a glucose-dependent manner. The GLP-1 receptor belongs to class B of the G-protein-coupled receptors, a subfamily characterized by a large N-terminal extracellular ligand binding domain. Exendin-4 and GLP-1 are 50% identical, and exendin-4 is a full agonist with similar affinity and potency for the GLP-1 receptor. We recently solved the crystal structure of the GLP-1 receptor extracellular domain in complex with the competitive antagonist exendin-4(9-39). Interestingly, the isolated extracellular domain binds exendin-4 with much higher affinity than the endogenous agonist GLP-1. Here, we have solved the crystal structure of the extracellular domain in complex with GLP-1 to 2.1 Aresolution. The structure shows that important hydrophobic ligand-receptor interactions are conserved in agonist- and antagonist-bound forms of the extracellular domain, but certain residues in the ligand-binding site adopt a GLP-1-specific conformation. GLP-1 is a kinked but continuous alpha-helix from Thr(13) to Val(33) when bound to the extracellular domain. We supplemented the crystal structure with site-directed mutagenesis to link the structural information of the isolated extracellular domain with the binding properties of the full-length receptor. The data support the existence of differences in the binding modes of GLP-1 and exendin-4 on the full-length GLP-1 receptor.
Department of GLP-1 and Obesity Biology, Novo Nordisk, 2760 Måløv, Denmark.
Christina Rye
CR
Underwood
Patrick
P
Garibay
Lotte Bjerre
LB
Knudsen
Sven
S
Hastrup
Günther H
GH
Peters
Rainer
R
Rudolph
Steffen
S
Reedtz-Runge
D000595:Amino Acid Sequence; D002460:Cell Line; D018360:Crystallography, X-Ray; D005110:Extracellular Space / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1 / Q000737:chemistry* / Q000378:metabolism; D000067757:Glucagon-Like Peptide-1 Receptor; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D018027:Receptors, Glucagon / Q000737:chemistry* / Q000378:metabolism; D012996:Solutions
C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D050505:Mutant Proteins; D018027:Receptors, Glucagon; D012996:Solutions; D052216:Glucagon-Like Peptide 1