Electrostatic steering at acetylcholine binding sites

Robert H. Meltzer, Errol Thompson, Kizhake V. Soman, Xing Zhi Song, Jerry O. Ebalunode, Theodore G. Wensel, James M. Briggs, Steen E. Pedersen

    Research output: Contribution to journalArticle

    17 Citations (Scopus)

    Abstract

    The electrostatic environments near the acetylcholine binding sites on the nicotinic acetylcholine receptor (nAChR) and acetylcholinesterase were measured by diffusion-enhanced fluorescence energy transfer (DEFET) to determine the influence of long-range electrostatic interactions on ligand binding kinetics and net binding energy. Changes in DEFET from variously charged Tb 3+-chelates revealed net potentials of -20 mV at the nAChR agonist sites and -14 mV at the entrance to the AChE active site, in physiological ionic strength conditions. The potential at the αδ-binding site of the nAChR was determined independently in the presence of d-tubocurarine to be -14 mV; the calculated potential at the αγ-site was approximately threefold stronger than at the αδ-site. By determining the local potential in increasing ionic strength, Debye-Hückel theory predicted that the potentials near the nAChR agonist binding sites are constituted by one to three charges in close proximity to the binding site. Examination of the binding kinetics of the fluorescent acetylcholine analog dansyl-C6-choline at ionic strengths from 12.5 to 400 mM revealed a twofold decrease in association rate. Debye-Hückel analysis of the kinetics revealed a similar charge distribution as seen by changes in the potentials. To determine whether the experimentally determined potentials are reflected by continuum electrostatics calculations, solutions to the nonlinear Poisson-Boltzmann equation were used to compute the potentials expected from DEFET measurements from high-resolution models of the nAChR and AChE. These calculations are in good agreement with the DEFET measurements for AChE and for the αγ-site of the nAChR. We conclude that long-range electrostatic interactions contribute -0.3 and -1 kcal/mol to the binding energy at the nAChR αδ- and αγ-sites due to an increase in association rates.

    Original languageEnglish (US)
    Pages (from-to)1302-1314
    Number of pages13
    JournalBiophysical Journal
    Volume91
    Issue number4
    DOIs
    StatePublished - 2006

    Fingerprint

    Nicotinic Receptors
    Static Electricity
    Acetylcholine
    Binding Sites
    Energy Transfer
    Fluorescence
    Osmolar Concentration
    Cholinergic Agonists
    Tubocurarine
    Acetylcholinesterase
    Catalytic Domain
    Ligands

    ASJC Scopus subject areas

    • Biophysics

    Cite this

    Meltzer, R. H., Thompson, E., Soman, K. V., Song, X. Z., Ebalunode, J. O., Wensel, T. G., ... Pedersen, S. E. (2006). Electrostatic steering at acetylcholine binding sites. Biophysical Journal, 91(4), 1302-1314. https://doi.org/10.1529/biophysj.106.081463

    Electrostatic steering at acetylcholine binding sites. / Meltzer, Robert H.; Thompson, Errol; Soman, Kizhake V.; Song, Xing Zhi; Ebalunode, Jerry O.; Wensel, Theodore G.; Briggs, James M.; Pedersen, Steen E.

    In: Biophysical Journal, Vol. 91, No. 4, 2006, p. 1302-1314.

    Research output: Contribution to journalArticle

    Meltzer, RH, Thompson, E, Soman, KV, Song, XZ, Ebalunode, JO, Wensel, TG, Briggs, JM & Pedersen, SE 2006, 'Electrostatic steering at acetylcholine binding sites', Biophysical Journal, vol. 91, no. 4, pp. 1302-1314. https://doi.org/10.1529/biophysj.106.081463
    Meltzer RH, Thompson E, Soman KV, Song XZ, Ebalunode JO, Wensel TG et al. Electrostatic steering at acetylcholine binding sites. Biophysical Journal. 2006;91(4):1302-1314. https://doi.org/10.1529/biophysj.106.081463
    Meltzer, Robert H. ; Thompson, Errol ; Soman, Kizhake V. ; Song, Xing Zhi ; Ebalunode, Jerry O. ; Wensel, Theodore G. ; Briggs, James M. ; Pedersen, Steen E. / Electrostatic steering at acetylcholine binding sites. In: Biophysical Journal. 2006 ; Vol. 91, No. 4. pp. 1302-1314.
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