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

This Article Full Text Full Text (PDF, 1980K) PPT slides of all figures Alert me when this article is cited Citation Map Services Email this article Similar articles in this journal Alert me to new content in the JGP Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Google Scholar Articles by Tang, Q. Articles by Bargiello, T. A. PubMed Articles by Tang, Q. Articles by Bargiello, T. A. Related Collections Related Article Social Bookmarking                            What's this?

¹ Dominic P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
² Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn, NY 11210

Correspondence to Thaddeus A. Bargiello: bargiell{at}aecom.yu.edu

The structure of the pore is critical to understanding the molecular mechanisms underlying selective permeation and voltage-dependent gating of channels formed by the connexin gene family. Here, we describe a portion of the pore structure of unapposed hemichannels formed by a Cx32 chimera, Cx32*Cx43E1, in which the first extracellular loop (E1) of Cx32 is replaced with the E1 of Cx43. Cysteine substitutions of two residues, V38 and G45, located in the vicinity of the border of the first transmembrane (TM) domain (TM1) and E1 are shown to react with the thiol modification reagent, MTSEA–biotin-X, when the channel resides in the open state. Cysteine substitutions of flanking residues A40 and A43 do not react with MTSEA–biotin-X when the channel resides in the open state, but they react with dibromobimane when the unapposed hemichannels are closed by the voltage-dependent "loop-gating" mechanism. Cysteine substitutions of residues V37 and A39 do not appear to be modified in either state. Furthermore, we demonstrate that A43C channels form a high affinity Cd²⁺ site that locks the channel in the loop-gated closed state. Biochemical assays demonstrate that A43C can also form disulfide bonds when oocytes are cultured under conditions that favor channel closure. A40C channels are also sensitive to micromolar Cd²⁺ concentrations when closed by loop gating, but with substantially lower affinity than A43C. We propose that the voltage-dependent loop-gating mechanism for Cx32*Cx43E1 unapposed hemichannels involves a conformational change in the TM1/E1 region that involves a rotation of TM1 and an inward tilt of either each of the six connexin subunits or TM1 domains.

© 2009 Tang et al.
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jgp.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

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

Related Article

Gating on the outside

Andrew L. Harris
J. Gen. Physiol. 2009 133: 549-553. [Full Text] [PDF]

This article has been cited by other articles:

				A. L. Harris Gating on the outside J. Gen. Physiol., June 1, 2009; 133(6): 549 - 553. [Full Text] [PDF]

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