Nuclear Magnetic Resonance Studies of Cannabinoid Receptor Site Peptides; Conference paper

摘要

Recent mutagenesis and chimera studies have implicated the second extracellular loops (E2) of CB1 and CB2 in ligand binding. As a contribution toward understanding the role of E2 in the interactions of CB1 and CB2 with cannabinoids, we have initiated structure studies on two E2 peptide analogues in the absence and presence of SDS using nuclear magnetic resonance (NMR) spectroscopy. Based on alpha proton chemical shifts, CB2-E2 and CB1-E2 have random coil conformations in an aqueous environment. The N-terminal half (residues E1-S8) of CB1-E2 in SDS micelles contains an alpha-helical stretch. CB2-E2 in the presence of SDS consists of at least two equally populated stable conformations, each having alpha proton chemical shifts consistent with random coil conformations. Preliminary simulated annealing calculations suggest that the E2 peptides in both the absence and presence of SDS contain a well-defined region that includes the CSXXXP sequence shared by the cannabinoid receptors and several orphan receptors. The precise conformation of the CSXXXP region depends on the peptide and the solvent system.