Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
XB-ART-14079
Biophys J 1998 Nov 01;755:2323-31.
Show Gene links Show Anatomy links

Localization of a voltage gate in connexin46 gap junction hemichannels.

Pfahnl A , Dahl G .


???displayArticle.abstract???
Cysteine replacement mutagenesis has identified positions in the first transmembrane domain of connexins as contributors to the pore lining of gap junction hemichannels (Zhou et al. 1997. Biophys. J. 72:1946-1953). Oocytes expressing a mutant cx46 with a cysteine in position 35 exhibited a membrane conductance sensitive to the thiol reagent maleimidobutyryl biocytin (MBB). MBB irreversibly reduced the single-channel conductance by 80%. This reactive cysteine was used to probe the localization of a voltage gate that closes cx46 gap junction hemichannels at negative potentials. MBB was applied to the closed channel either from outside (whole cell) or from inside (excised membrane patches). After washout of the thiol reagent the channels were tested at potentials at which the channels open. After extracellular application of MBB to intact oocytes, the membrane conductance was unaffected. In contrast, channels treated with intracellular MBB were blocked. Thus the cysteine in position 35 of cx46 is accessible from inside but not from the outside while the channel is closed. These results suggest that the voltage gate, which may be identical to the "loop gate" (Trexler et al. 1996. Proc. Natl. Acad. Sci. USA. 93:5836-5841), is located extracellular to the 35 position. The voltage gate results in regional closure of the pore rather than closure along the entire pore length.

???displayArticle.pubmedLink??? 9788927
???displayArticle.pmcLink??? PMC1299906
???displayArticle.link??? Biophys J
???displayArticle.grants??? [+]

Species referenced: Xenopus
Genes referenced: gja3 tbx2

References [+] :
Armstrong, Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons. 1971, Pubmed