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XB-ART-14081
Biophys J 1998 Nov 01;755:2292-301.
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Subunit stoichiometry of a core conduction element in a cloned epithelial amiloride-sensitive Na+ channel.

Berdiev BK , Karlson KH , Jovov B , Ripoll PJ , Morris R , Loffing-Cueni D , Halpin P , Stanton BA , Kleyman TR , Ismailov II .


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The molecular composition of a core conduction element formed by the alpha-subunit of cloned epithelial Na+ channels (ENaC) was studied in planar lipid bilayers. Two pairs of in vitro translated proteins were employed in combinatorial experiments: 1) wild-type (WT) and an N-terminally truncated alphaDeltaN-rENaC that displays accelerated kinetics (tauo = 32 +/- 13 ms, tauc = 42 +/- 11 ms), as compared with the WT channel (tauc1 = 18 +/- 8 ms, tauc2 = 252 +/- 31 ms, and tauo = 157 +/- 43 ms); and 2) WT and an amiloride binding mutant, alphaDelta278-283-rENaC. The channels that formed in a alphaWT:alphaDeltaN mixture fell into two groups: one with tauo and tauc that corresponded to those exhibited by the alphaDeltaN-rENaC alone, and another with a double-exponentially distributed closed time and a single-exponentially distributed open time that corresponded to the alphaWT-rENaC alone. Five channel subtypes with distinct sensitivities to amiloride were found in a 1alphaWT:1alphaDelta278-283 protein mixture. Statistical analyses of the distributions of channel phenotypes observed for either set of the WT:mutant combinations suggest a tetrameric organization of alpha-subunits as a minimal model for the core conduction element in ENaCs.

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References [+] :
Awayda, Regulation of a cloned epithelial Na+ channel by its beta- and gamma-subunits. 1997, Pubmed, Xenbase