We used cell lines expressing wild-type connexin43 and connexin43 fused with the enhanced green fluorescent protein (Cx43-EGFP) to examine conductance and perm-selectivity of the residual state of Cx43 homotypic and Cx43/Cx43-EGFP heterotypic gap junction channels. Each hemichannel in Cx43 cell–cell channel possesses two gates: a fast gate that closes channels to the residual state and a slow gate that fully closes channels; the transjunctional voltage (Vj) closes the fast gate in the hemichannel that is on the relatively negative side. Here, we demonstrate macroscopically and at the single-channel level that the I-V relationship of the residual state rectifies, exhibiting higher conductance at higher Vjs that are negative on the side of gated hemichannel. The degree of rectification increases when Cl− is replaced by Asp− and decreases when K+ is replaced by TEA+. These data are consistent with an increased anionic selectivity of the residual state. The Vj-gated channel is not permeable to monovalent positively and negatively charged dyes, which are readily permeable through the fully open channel. These data indicate that a narrowing of the channel pore accompanies gating to the residual state. We suggest that the fast gate operates through a conformational change that introduces positive charge at the cytoplasmic vestibule of the gated hemichannel, thereby producing current rectification, increased anionic selectivity, and a narrowing of channel pore that is largely responsible for reducing channel conductance and restricting dye transfer. Consequently, the fast Vj-sensitive gating mechanism can serve as a selectivity filter, which allows electrical coupling but limits metabolic communication.
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1 February 2002
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January 28 2002
Conductance and Permeability of the Residual State of Connexin43 Gap Junction Channels
Feliksas F. Bukauskas,
Feliksas F. Bukauskas
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
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Angele Bukauskiene,
Angele Bukauskiene
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
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Vytas K. Verselis
Vytas K. Verselis
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
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Feliksas F. Bukauskas
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
Angele Bukauskiene
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
Vytas K. Verselis
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
Address correspondence to F. Bukauskas, 1300 Morris Park Avenue, Bronx, NY 10461. Fax: (718) 430-8944. E-mail: [email protected]
*
Abbreviations used in this paper: CT, COOH termini; Cx, connexin; EGFP, enhanced green fluorescent protein; GJ, gap junction; gj, junctional conductance; NT, NH2 termini; PNP, Poisson-Nernst-Plank; vj, transjunctional voltage.
Received:
November 08 2001
Revision Received:
December 31 2001
Accepted:
January 03 2002
Online ISSN: 1540-7748
Print ISSN: 0022-1295
The Rockefeller University Press
2002
J Gen Physiol (2002) 119 (2): 171–186.
Article history
Received:
November 08 2001
Revision Received:
December 31 2001
Accepted:
January 03 2002
Citation
Feliksas F. Bukauskas, Angele Bukauskiene, Vytas K. Verselis; Conductance and Permeability of the Residual State of Connexin43 Gap Junction Channels . J Gen Physiol 1 February 2002; 119 (2): 171–186. doi: https://doi.org/10.1085/jgp.119.2.171
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