Differential Structural Properties of Glp-1 and Exendin-4 Determine Their Relative Affinity for the Glp-1 Receptor N-terminal Extracellular Domain.
From: Department of Structure and Biophysical Chemistry, Novo Nordisk, DK-2880 Bagsvaerd, Denmark. sffr@novonordisk.com
Biochemistry
- Publish Date: May 2007
- ISSN: 0006-2960
- Volume: 46
- Issue: 19
- Pages: 5830-40
- Medium: Print
- Language: English
- Citation (JAMA): Runge Steffen, Schimmer Susann, Oschmann Jan, et al. Differential Structural Properties of Glp-1 and Exendin-4 Determine Their Relative Affinity for the Glp-1 Receptor N-terminal Extracellular Domain.. Biochemistry May 2007;46:5830-40
Abstract
Glucagon-like peptide-1 (GLP-1) and exendin-4 (Ex4) are homologous peptides with established potential for treatment of type 2 diabetes. They bind and activate the pancreatic GLP-1 receptor (GLP-1R) with similar affinity and potency and thereby promote insulin secretion in a glucose-dependent manner. GLP-1R belongs to family B of the seven transmembrane G-protein coupled receptors. The N-terminal extracellular domain (nGLP-1R) is a ligand binding domain with differential affinity for Ex4 and GLP-1: low affinity for GLP-1 and high affinity for exendin-4. The superior affinity of nGLP-1R for Ex4 was previously explained by an additional interaction between nGLP-1R and the C-terminal Trp-cage of Ex4. In this study we have combined biophysical and pharmacological approaches thus relating structural properties of the ligands in solution to their relative binding affinity for nGLP-1R. We used both a tracer competition assay and ligand-induced thermal stabilization of nGLP-1R to measure the relative affinity of full length, truncated, and chimeric ligands for soluble refolded nGLP-1R. The ligands in solution and the conformational consequences of ligand binding to nGLP-1R were characterized by circular dichroism and fluorescence spectroscopy. We found a correlation between the helical content of the free ligands and their relative binding affinity for nGLP-1R, supporting the hypothesis that the ligands are helical at least in the segment that binds to nGLP-1R. The Trp-cage of Ex4 was not necessary to maintain a superior helicity of Ex4 compared to GLP-1. The results suggest that the differential affinity of nGLP-1R is explained almost entirely by divergent residues in the central part of the ligands: Leu10-Gly30 of Ex4 and Val16-Arg36 of GLP-1. In view of our results it appears that the Trp-cage plays only a minor role for the interaction between Ex4 and nGLP-1R and for the differential affinity of nGLP-1R for GLP-1 and Ex4.
Mesh Headings (Keywords): Amino Acid Sequence, Animals, Calorimetry, Differential Scanning, Circular Dichroism, Cricetinae, Glucagon-Like Peptide 1, Heat, Humans, Ligands, Molecular Sequence Data, Peptides, Protein Denaturation, Protein Folding, Protein Structure, Tertiary, Receptors, Glucagon, Sequence Alignment, Spectrometry, Fluorescence, Venoms
Check for Full Text / PubMed Unique Identifier (PMID): 17444618
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