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Functional Dynamics of Cysteines in the Epithelial Na + Channel Finger Domains
Author(s) -
Blobner Brandon Michael,
Kashlan Ossama B
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1223.10
Subject(s) - epithelial sodium channel , acid sensing ion channel , chemistry , cysteine , protein subunit , ring finger domain , ion channel , biophysics , zinc finger , extracellular , biochemistry , biology , transcription factor , sodium , enzyme , gene , receptor , organic chemistry
The epithelial Na + channel (ENaC) is a member of the ENaC/Degenerin family of ion channels. The structure of one member of this protein family, acid sensing ion channel 1 (ASIC1), has been resolved. ASIC1 shares high sequence homology with ENaC. ENaC has a set of cysteines in the extracellular domains of each subunit that form disulphide bonds, as is characteristic of this protein family. ENaC subunits contain an additional pair of cysteines in the poorly conserved extracellular finger domains that are not present in ASIC1. The disposition of these cysteines is unclear. Using bifunctional methanethiosulfonate (MTS) crosslinkers and the oxidizing agent copper phenanthroline, we probed the region surrounding the finger domain cysteines. Our data shows that the finger domain cysteines of both the alpha and gamma subunits are positioned in close proximity to the finger‐thumb domain interface of the respective subunits. Crosslinking to these cysteines affected ENaC currents, suggesting mechanical linkage between this peripheral site and the channel gate. Our data also shows that removal of either gamma finger domain cysteine results in the loss of irreversible ENaC inhibition by MTS reagents, an affect that we previously reported. Our data suggests that ENaC finger domain cysteines may be experimentally modified in a manner that regulates ENaC activity. Support or Funding Information This work is supported by NIH grants DK098204 and DK061296‐12.