2001
DOI: 10.1085/jgp.118.6.679
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Permeability Properties of Enac Selectivity Filter Mutants

Abstract: The epithelial Na+ channel (ENaC), located in the apical membrane of tight epithelia, allows vectorial Na+ absorption. The amiloride-sensitive ENaC is highly selective for Na+ and Li+ ions. There is growing evidence that the short stretch of amino acid residues (preM2) preceding the putative second transmembrane domain M2 forms the outer channel pore with the amiloride binding site and the narrow ion-selective region of the pore. We have shown previously that mutations of the αS589 residue in the preM2 segment… Show more

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Cited by 71 publications
(76 citation statements)
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“…These functional results together with the highly conserved sequence of M2 support the view that M2 forms the ion pathway (17,18). Although the region preceding M1 has also been implicated in ion permeation (11), we found little correlation of the poorly conserved amino termini with the pore properties.…”
Section: Structural and Functional Comparison Of Fish And Ratsupporting
confidence: 79%
“…These functional results together with the highly conserved sequence of M2 support the view that M2 forms the ion pathway (17,18). Although the region preceding M1 has also been implicated in ion permeation (11), we found little correlation of the poorly conserved amino termini with the pore properties.…”
Section: Structural and Functional Comparison Of Fish And Ratsupporting
confidence: 79%
“…These findings are most easily explained by gua ϩ transiting the pathway through the exclusive Na ϩ site as proposed by Li et al (21). This novel effect of gua ϩ (mean geometric diameter, 4.4 Å) (31) sets minimal dimensions to the access channel normally transited by the first Na ϩ ion released from the exclusive site, indicating that Na ϩ may move in a hydrated form similar to proposals for Na ϩ permeation through VNaC (25). Although our data suggest that this pathway cannot accommodate NMG ϩ (mean diameter 7.3 Å) (32), consistent with the inability of NMG ϩ to inhibit the pump in a voltagedependent manner, we cannot be sure whether this access channel is narrower than the pathway opened by palytoxin on the Na/K-ATPase (33).…”
Section: Discussionmentioning
confidence: 99%
“…Guanidinium ϩ (gua ϩ ) ions compete with Na i ϩ for binding to the Na/K pump (23) and have been shown to permeate voltagedependent Na ϩ channels [VNaC (24), but not epithelial Na ϩ channels (25)]. To test whether gua ϩ is a Na ϩ -surrogate and can sustain inward currents through truncated pumps, we measured ouabain-sensitive currents with 120 mM gua o ϩ (Fig.…”
Section: Effects On Na Omentioning
confidence: 99%
“…6c,d). Such a significant change in the geometry of the selectivity filter is an exception in the field of ion channels in particularly, because molecular sieving has been proposed as the basis for selecting Na + over K + in channels of the ENaC/Degenerins family [16][17][18] . It is unexpected that a channel that may rely on pore size to select the passing ions is also one that exhibits major changes in the diameter of the selectivity filter during gating.…”
Section: Discussionmentioning
confidence: 99%