Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents

This Article Full Text Full Text (PDF, 133K) PPT slides of all figures Alert me when this article is cited Citation Map Services Email this article Similar articles in this journal Similar articles in PubMed Alert me to new content in the JGP Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Bouzat, C. Articles by Sine, S. Search for Related Content PubMed PubMed Citation Articles by Bouzat, C. Articles by Sine, S. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Social Bookmarking                            What's this?

Original Article

Hydrogen Bonding by Conserved Threonine Contributes to Channel Gating Kinetics

Cecilia Bouzat^a, Francisco Barrantes^a, and Steven Sine^b

^a From the Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, 8000 Bahía Blanca, Argentina
^b Receptor Biology Laboratory, Department of Physiology and Biophysics, Mayo Foundation, Rochester, Minnesota 55905
Instituto de Investigaciones Bioquímicas, UNS-CONICET, Camino La Carrindanga Km 7, 8000 Bahía Blanca, Argentina.54-291-4861201

inbouzat{at}criba.edu.ar

The fourth transmembrane domain (M4) of the nicotinic acetylcholine receptor (AChR) contributes to the kinetics of activation, yet its close association with 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 T422, 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 T422 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 T422 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.

Key Words: patch clamp • kinetic analysis • nicotinic acetylcholine receptor channel gating • fourth transmembrane domain • hydrogen bond

CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents