NMR resolved multiple anesthetic binding sites in the TM domains of the ?4?2 nAChR.

ABSTRACT: The ?4?2 nicotinic acetylcholine receptor (nAChR) has significant roles in nervous system function and disease. It is also a molecular target of general anesthetics. Anesthetics inhibit the ?4?2 nAChR at clinically relevant concentrations, but their binding sites in ?4?2 remain unclear. The recently determined NMR structures of the ?4?2 nAChR transmembrane (TM) domains provide valuable frameworks for identifying the binding sites. In this study, we performed solution NMR experiments on the ?4?2 TM domains in the absence and presence of halothane and ketamine. Both anesthetics were found in an intra-subunit cavity near the extracellular end of the ?2 transmembrane helices, homologous to a common anesthetic binding site observed in X-ray structures of anesthetic-bound GLIC (Nury et al., [32]). Halothane, but not ketamine, was also found in cavities adjacent to the common anesthetic site at the interface of ?4 and ?2. In addition, both anesthetics bound to cavities near the ion selectivity filter at the intracellular end of the TM domains. Anesthetic binding induced profound changes in protein conformational exchanges. A number of residues, close to or remote from the binding sites, showed resonance signal splitting from single to double peaks, signifying that anesthetics decreased conformation exchange rates. It was also evident that anesthetics shifted population of two conformations. Altogether, the study comprehensively resolved anesthetic binding sites in the ?4?2 nAChR. Furthermore, the study provided compelling experimental evidence of anesthetic-induced changes in protein dynamics, especially near regions of the hydrophobic gate and ion selectivity filter that directly regulate channel functions.

SUBMITTER: Bondarenko V 

PROVIDER: S-EPMC3534943 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature