X-Ray Crystallographic Studies for Revealing Binding Sites of General Anesthetics in Pentameric Ligand-Gated Ion Channels

Abstract

X-ray crystallography is a powerful tool in structural biology and can offer insight into structured-based understanding of general anesthetic action on various relevant molecular targets, including pentameric ligand-gated ion channels (pLGICs). In this chapter, we outline the procedures for expression and purification of pLGICs. Optimization of crystallization conditions, especially to achieve high-resolution structures of pLGICs bound with general anesthetics, is also presented. Case studies of pLGICs bound with the volatile general anesthetic isoflurane, 2-bromoethanol, and the intravenous general anesthetic ketamine are revisited.

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“…The existence of spatially-defined cavities (i.e., presumptive functional binding sites) that can accommodate small anesthetic molecules have been identified in a variety of proteins, including firefly luciferase, human serum albumin, and both ligand-and voltage-gated ion channels [55][56][57]. Modeling based on molecular mechanics-quantum mechanics calculations suggest that anesthetic-protein complexes share a set of common characteristics, or "binding motifs"; these motifs are "polar and nonpolar interactions within an amphiphilic binding cavity, including the presence of weak hydrogen bond interactions with amino acids and water molecules" [58].…”