title: Glucagon and glucagon-like peptide 1: selective receptor recognition via distinct peptide epitopes.
abstract: Glucagon and glucagon-like peptide 1 (GLP-1) are homologous peptide hormones that are recognized by likewise homologous, but highly selective receptors. Analogs of glucagon and GLP-1, in which the divergent residues were systematically exchanged, were employed to identify the structural requirements for their selective receptor recognition. Substitutions in the NH2-terminal part of the glucagon molecule with the corresponding GLP-1 residues, as for example in [Ala2,Glu3]-glucagon and [Val10,Ser12]glucagon, reduced the binding affinity for the glucagon receptor several hundred-fold without increasing the affinity for the GLP-1 receptor. In contrast, introduction of GLP-1 residues into the far COOH-terminal part of the glucagon molecule, e.g. [Val27,Lys28,Gly29,Arg30]glucagon, had a minimal effect on recognition of the glucagon receptor, but improved the affinity of the analog for the GLP-1 receptor up to 200-fold. Similarly, substitutions in especially the far COOH-terminal part of the GLP-1 molecule with the corresponding glucagon residues, e.g. des-Arg30-[Met27,Asn28,Thr29]GLP-1, decreased the affinity for the GLP-1 receptor several hundred-fold (IC50 = 0.4-190 nM) without increasing the affinity for the glucagon receptor. Conversely, substitutions in the NH2-terminal part of the GLP-1 molecule impaired the affinity for the GLP-1 receptor only moderately. We conclude that the selective recognition of the glucagon and GLP-1 receptors is determined by residues located at opposite ends of the homologous peptide ligands. This conclusion is supported by the observation that a "chimeric" peptide consisting of the NH2-terminal part of the glucagon molecule joined to the COOH-terminal part of the GLP-1 molecule was recognized with high affinity by both receptors.
authors.affiliation: Laboratory for Molecular Endocrinology, Rigshospitalet, Copenhagen, Denmark.
authors.forename: S A
authors.initials: SA
authors.lastname: Hjorth
authors.forename: K
authors.initials: K
authors.lastname: Adelhorst
authors.forename: B B
authors.initials: BB
authors.lastname: Pedersen
authors.forename: O
authors.initials: O
authors.lastname: Kirk
authors.forename: T W
authors.initials: TW
authors.lastname: Schwartz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism*; D005934:Glucagon / Q000031:analogs & derivatives / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D011498:Protein Precursors / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D018027:Receptors, Glucagon / Q000378:metabolism*; D013552:Swine
chemical_list: D000939:Epitopes; D010446:Peptide Fragments; D010455:Peptides; D011498:Protein Precursors; D018027:Receptors, Glucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon