Curariform antagonists bind in different orientations to acetylcholine-binding protein

Fan Gao, Nina Bren, Alicia Little, Hai Long Wang, Scott B. Hansen, Todd T. Talley, Palmer Taylor, Steven M. Sine

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Acetylcholine-binding protein (AChBP) recently emerged as a prototype for relating structure to function of the ligand binding domain of nicotinic acetylcholine receptors (AChRs). To understand interactions of competitive antagonists at the atomic structural level, we studied binding of the curare derivatives d-tubocurarine (d-TC) and metocurine to AChBP using computational methods, mutagenesis, and ligand binding measurements. To account for protein flexibility, we used a 2-ns molecular dynamics simulation of AChBP to generate multiple snapshots of the equilibrated dynamic structure to which optimal docking orientations were determined. Our results predict a predominant docking orientation for both d-TC and metocurine, but unexpectedly, the bound orientations differ fundamentally for each ligand. At one subunit interface of AChBP, the side chain of Tyr-89 closely approaches a positively charged nitrogen in d-TC but is farther away from the equivalent nitrogen in metocurine, whereas, at the opposing interface, side chains of Trp-53 and Gln-55 closely approach the metocurine scaffold but not that of d-TC. The different orientations correspond to ∼170° rotation and ∼30° degree tilt of the curare scaffold within the binding pocket. Mutagenesis of binding site residues in AChBP, combined with measurements of ligand binding, confirms the different docking orientations. Thus structurally similar ligands can adopt distinct orientations at receptor binding sites, posing challenges for interpreting structure-activity relationships for many drugs.

Original languageEnglish (US)
Pages (from-to)23020-23026
Number of pages7
JournalJournal of Biological Chemistry
Volume278
Issue number25
DOIs
StatePublished - Jun 20 2003

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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