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Conserved amino acids in the pre‐TM1 region of the ENaC/Deg ion channel superfamily are important for gating
Author(s) -
Kucher Volodymyr,
Boiko Nina,
Pochynyuk Oleh,
Stockand James D.
Publication year - 2011
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.25.1_supplement.860.3
Subject(s) - epithelial sodium channel , transmembrane domain , gating , heterologous expression , acid sensing ion channel , allosteric regulation , conserved sequence , chemistry , protein subunit , amino acid , pseudohypoaldosteronism , extracellular , ion channel , biophysics , biochemistry , function (biology) , peptide sequence , transmembrane protein , biology , microbiology and biotechnology , recombinant dna , enzyme , gene , receptor , organic chemistry , sodium
All members of the ENaC/Deg superfamily contain a conserved His‐Gly sequence in their NH 2 ‐terminus. Substitution of the conserved Gly results in loss of function leading to the salt wasting disorder pseudohypoaldosteronism type I. The exact role of these conserved residues to ENaC function, though, remains largely unknown. Similarly, understanding of structure‐function relations for cytoplasmic domains in ENaC/Deg channels is not as developed as it is for transmembrane and extracellular domains for which there is good crystallographic data. By combining the patch clamp method with heterologous expression of ENaC containing point mutations in these residues, we found that substitution of these critical amino acids dramatically decreases ENaC P o and leads to voltage‐sensing where P o increasing as a function of hyperpolarizing potentials. A functional element, including or near these critical residues, located on the intracellular side of the membrane must interact in an allosteric manner with the channel gate or be part of the gate to produce these results. Voltage‐sensing and loss of function upon substitution of these critical residues are species and subunit independent arguing that this putative functional element is common to all ENaC subunits and possibly all ENaC/Deg subunits. Our results are most consistent with the cytoplasmic domains of ENaC developing important structure that impacts function.