Receptor-bound conformation of cilengitide better represented by its solution-state structure than the solid-state...

Area of Science:

• Medicinal Chemistry
• Structural Biology
• Pharmacology

Background:

• Peptide drug candidates like Cilengitide (cyclo(RGDf(NMe)Val)) are designed to target specific receptors.
• Understanding ligand conformation is critical for predicting and optimizing drug-receptor interactions.

Purpose of the Study:

• To compare the solution and crystal structures of Cilengitide.
• To evaluate how different conformations affect binding to the integrin αvβ3 receptor.
• To assess the implications for structure-based drug design.

Main Methods:

• X-ray crystallography to determine solid-state structure.
• Nuclear Magnetic Resonance (NMR) spectroscopy for solution structures.
• Molecular modeling and docking studies to simulate ligand-receptor interactions.

Main Results:

• Solution structures of Cilengitide closely matched the integrin αvβ3-bound conformation.
• The crystal structure of Cilengitide showed a different conformation influenced by crystal packing forces.
• Molecular modeling indicated that the crystal conformation led to a poor fit with the integrin receptor.

Conclusions:

• Discrepancies between solution and crystal conformations of Cilengitide exist.
• Relying solely on crystal structures for drug design may be misleading.
• Ligand conformation in different states must be carefully considered in drug optimization.