The dynamics of the G protein-coupled neuropeptide Y2 receptor in monounsaturated membranes investigated by solid-state NMR spectroscopy

In contrast to the static snapshots provided by protein crystallography, G protein-coupled receptors constitute a group of proteins with highly dynamic properties, which are required in the receptors' function as signaling molecule. Here, the human neuropeptide Y2 receptor was reconstituted into a model membrane composed of monounsaturated phospholipids and solid-state NMR was used to characterize its dynamics. Qualitative static N-15 NMR spectra and quantitative determination of H-1-C-13 order parameters through measurement of the H-1-C-13 dipolar couplings of the CH, CH2 and CH3 groups revealed axially symmetric motions of the whole molecule in the membrane and molecular fluctuations of varying amplitude from all molecular segments. The molecular order parameters (S-backbone = 0.59-0.67, S-CH2 = 0.41-0.51 and S-CH3 = 0.22) obtained in directly polarized C-13 NMR experiments demonstrate that the Y2 receptor is highly mobile in the native-like membrane. Interestingly, according to these results the receptor was found to be slightly more rigid in the membranes formed by the monounsaturated phospholipids than by saturated phospholipids as investigated previously. This could be caused by an increased chain length of the monounsaturated lipids, which may result in a higher helical content of the receptor. Furthermore, the incorporation of cholesterol, phosphatidylethanolamine, or negatively charged phosphatidylserine into the membrane did not have a significant influence on the molecular mobility of the Y2 receptor.