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Block of Kcnk3 by Protons
KCNK subunits have two pore-forming P domains and four predicted transmembrane segments. To assess the number of subunits in each pore, we studied external proton block of Kcnk3, a subunit prominent in rodent heart and brain. Consistent with a pore-blocking mechanism, inhibition was dependent on vol...
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Published in: | The Journal of biological chemistry 2001-07, Vol.276 (27), p.24449-24452 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | KCNK subunits have two pore-forming P domains and four predicted transmembrane segments. To assess the number of subunits
in each pore, we studied external proton block of Kcnk3, a subunit prominent in rodent heart and brain. Consistent with a
pore-blocking mechanism, inhibition was dependent on voltage, potassium concentration, and a histidine in the first P domain
(P1H). Thus, at pH 6.8 with 20 m m potassium half the current passed by P1H channels was blocked (apparently via two sites â¼10% into the electrical field) whereas
channels with an asparagine substitution (P1N) were fully active. Furthermore, pore blockade by barium was sensitive to pH
in P1H but not P1N channels. Although linking two Kcnk3 subunits in tandem to produce P1H-P1H and P1N-P1N channels bearing
four P domains did not alter these attributes, the mixed tandems P1H-P1N and P1N-P1H were half-blocked at pH â¼6.4, apparently
via a single site. This implicates a dimeric structure for Kcnk3 channels with two (and only two) P1 domains in each pore
and argues that P2 domains also contribute to pore formation. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.C100184200 |