Toward atomic-scale understanding of ligand recognition in the muscle nicotinic receptor

Steven M. Sine, Hai Long Wang, Fao Gao

Research output: Contribution to journalReview article

15 Scopus citations

Abstract

The nicotinic receptor at the motor endplate has served as a prototype for understanding structure, function and ligand recognition in the superfamily of pentameric ligand-gated ion channels. Yet despite this advanced state of knowledge, atomic-scale understanding of such elementary processes as ligand recognition has remained elusive owing to the lack of a high-resolution x-ray structure. However, the field has recently entered a state of rapid advancement following the discovery and atomic structural determination of the water-soluble acetylcholine binding protein (AChBP), a homolog of the receptor ligand binding domain. The AChBP structure provides the theoretical foundation for generating homology models of the corresponding receptor ligand binding domains within this structural family of receptors. Experimental assignment of residue equivalence between AChBP and receptor subunits subsequently yielded homology models ready for experimental testing. One such test is computational determination of ligand docking orientation in conjunction with mutagenesis of predicted contact residues and measurements of ligand binding affinity. Applied to different analogs of the competitive antagonist curare, docking computations that incorporate intrinsic protein flexibility reveal fundamentally distinct orientations of each analog bound to AChBP. The different contact residues predicted for each analog were tested and confirmed by mutagenesis of AChBP followed by measurements of ligand binding. By applying the same computational and experimental approaches to the adult human muscle AChR, we find that the two curare analogs also dock in distinctly different orientations. Thus subtle structural changes in the ligand, and by extension, structural differences in non-conserved residues among receptor subtypes and species, can dramatically alter the orientation of the bound ligand. The results have important implications for design of drugs targeting nicotinic receptors and members of the superfamily of pentameric ligand-gated ion channels.

Original languageEnglish (US)
Pages (from-to)559-567
Number of pages9
JournalCurrent Medicinal Chemistry
Volume11
Issue number5
DOIs
StatePublished - Mar 1 2004

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Keywords

  • Acetylcholine receptor and binding protein
  • Curariform antagonists
  • Flexible ligand docking
  • Mutagenesis-based homology model

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Pharmacology
  • Drug Discovery
  • Organic Chemistry

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