Identification of amino acid residues lining the pore of a gap junction channel
Open Access
- 28 October 2002
- journal article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 159 (2), 349-360
- https://doi.org/10.1083/jcb.200207060
Abstract
Gap junctions represent a ubiquitous and integral part of multicellular organisms, providing the only conduit for direct exchange of nutrients, messengers and ions between neighboring cells. However, at the molecular level we have limited knowledge of their endogenous permeants and selectivity features. By probing the accessibility of systematically substituted cysteine residues to thiol blockers (a technique called SCAM), we have identified the pore-lining residues of a gap junction channel composed of Cx32. Analysis of 45 sites in perfused Xenopus oocyte pairs defined M3 as the major pore-lining helix, with M2 (open state) or M1 (closed state) also contributing to the wider cytoplasmic opening of the channel. Additional mapping of a close association between M3 and M4 allowed the helices of the low resolution map (Unger et al., 1999. Science. 283:1176–1180) to be tentatively assigned to the connexin transmembrane domains. Contrary to previous conceptions of the gap junction channel, the residues lining the pore are largely hydrophobic. This indicates that the selective permeabilities of this unique channel class may result from novel mechanisms, including complex van der Waals interactions of permeants with the pore wall, rather than mechanisms involving fixed charges or chelation chemistry as reported for other ion channels.Keywords
This publication has 37 references indexed in Scilit:
- The open pore conformation of potassium channelsNature, 2002
- Unique and Redundant Connexin Contributions to Lens DevelopmentScience, 2002
- Human diseases: clues to cracking the connexin code?Trends in Cell Biology, 2001
- The Structure of the Potassium Channel: Molecular Basis of K + Conduction and SelectivityScience, 1998
- Structure of gap junction intercellular channelsCurrent Opinion in Structural Biology, 1996
- Identification of a proline residue as a transduction element involved in voltage gating of gap junctionsNature, 1993
- Site-directed mutagenesis by overlap extension using the polymerase chain reactionGene, 1989
- Molecular cloning of cDNA for rat liver gap junction protein.The Journal of cell biology, 1986
- Evidence for fixed charge in the nexusNature, 1980
- Structure and biochemistry of mouse hepatic gap junctionsJournal of Molecular Biology, 1979