At least three xenon binding sites in the glycine binding domain of the N-methyl D-aspartate receptor

Xenon can produce general anesthesia. Its main protein target is the N-methyl-D-aspartate receptor, a ionotropic channel playing a pivotal role in the function of the central nervous system. The molecular mechanisms allowing this noble gas to have such a specific effect remain obscure, probably as a consequence of the lack of structural data at the atomic level of detail. As a result of five independent molecular dynamics simulations, three different binding sites were found for xenon in the glycine binding domain of the N-methyl-D-aspartate receptor, the xenon binding constant being of the order of 2 108 s(-1).M-1. On the other hand, the absolute binding free energy of xenon in these sites ranges between-3 and 14 kJ.mole(-1). Noteworthy, it depends significantly upon the protein conformer chosen for performing the calculation, suggesting that larger values could be obtained, if other conformers were considered. These three sites are next to each other, one of them being next to the glycine site. This could noteworthy explain why the F758W and F758Y mutations can prevent competitive inhibition by xenon without affecting glycine binding.