Nicotinic receptor fourth transmembrane domain: Hydrogen bonding by conserved threonine contributes to channel gating kinetics

Cecilia Bouzat, Francisco Barrantes, Steven Sine

Research output: Contribution to journalArticle

77 Scopus citations

Abstract

The fourth transmembrane domain (M4) of the nicotinic acetylcholine receptor (AChR) contributes to the kinetics of activation, yet its close association width the lipid bilayer makes it the outermost of the transmembrane domains. To investigate mechanistic and structural contributions of M4 to AChR activation, we systematically mutated αT422, a conserved residue that has been labeled by hydrophobic probes, and evaluated changes in rate constants underlying ACh binding and channel gating steps. Aromatic and nonpolar mutations of αT422 selectively affect the channel gating step, slowing the rate of opening two- to sevenfold, and speeding the rate of closing four- to ninefold. Additionally, kinetic modeling shows a second doubly liganded open state for aromatic and nonpolar mutations. In contrast, serine and asparagine mutations of αT422 largely preserve the kinetics of the wild-type AChR. Thus, rapid and efficient gating of the AChR channel depends on a hydrogen bond involving the side chain at position 422 of the M4 transmembrane domain.

Original languageEnglish (US)
Pages (from-to)663-671
Number of pages9
JournalJournal of General Physiology
Volume115
Issue number5
DOIs
StatePublished - May 1 2000

Keywords

  • Fourth transmembrane domain
  • Hydrogen bond
  • Kinetic analysis
  • Nicotinic acetylcholine receptor channel gating
  • Patch clamp

ASJC Scopus subject areas

  • Physiology

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