Cysteine Mapping in the Ion Selectivity and Toxin Binding Region of the Cardiac Na+ Channel Pore

Cysteine Mapping in the Ion Selectivity and Toxin Binding Region of the Cardiac Na+ Channel Pore Aqueous exposure of critical residues in the selectivity region of voltage gated Na+ channels was studied by cysteine-scanning mutagenesis at three positions in each of the SS2 segments of domains III (D3) and IV (D4) of the human heart Na+ channel. Ionic currents were modified by charged cysteine-specific methanethiosulfonate (MTS) reagents, (2-aminoethyl)methanethiosulfonate (MTSEA+) and (2-sulfonatoethyl)methanethiosulfonate (MTSES−) in all six of the Cys-substituted channels, including Trp → Cys substitutions at homologous positions in D3 and D4 that were predicted in secondary structure models to have buried side chains. Furthermore, in the absence of MTS modification, each of the Cys mutants showed a reduction in tetrodotoxin (TTX) block by a factor >102. Cysteine substitution without MTS modification abolished the alkali metal ion selectivity in K1418C (D3), but not in A1720C (the corresponding position in D4) suggesting that the lysine but not the alanine side chains contribute to selectivity even though both were exposed. Neither position responded to MTSES− suggesting that these residues occupy either a size- or charge-restricted region of the pore. By contrast, MTSES− markedly increased, and MTSEA+ markedly decreased conductance of D1713C (D4) suggesting that the acidic side chain of Asp1713 acts electrostatically in an unrestricted region. These results suggest that Lys1418 lies in a restricted region favorable to cations, whereas Asp1713 is at a more peripheral location in the Na+ channel pore. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Cysteine Mapping in the Ion Selectivity and Toxin Binding Region of the Cardiac Na+ Channel Pore

Loading next page...
 
/lp/springer_journal/cysteine-mapping-in-the-ion-selectivity-and-toxin-binding-region-of-fGjIq5B0ma
Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1997 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900154
Publisher site
See Article on Publisher Site

Abstract

Aqueous exposure of critical residues in the selectivity region of voltage gated Na+ channels was studied by cysteine-scanning mutagenesis at three positions in each of the SS2 segments of domains III (D3) and IV (D4) of the human heart Na+ channel. Ionic currents were modified by charged cysteine-specific methanethiosulfonate (MTS) reagents, (2-aminoethyl)methanethiosulfonate (MTSEA+) and (2-sulfonatoethyl)methanethiosulfonate (MTSES−) in all six of the Cys-substituted channels, including Trp → Cys substitutions at homologous positions in D3 and D4 that were predicted in secondary structure models to have buried side chains. Furthermore, in the absence of MTS modification, each of the Cys mutants showed a reduction in tetrodotoxin (TTX) block by a factor >102. Cysteine substitution without MTS modification abolished the alkali metal ion selectivity in K1418C (D3), but not in A1720C (the corresponding position in D4) suggesting that the lysine but not the alanine side chains contribute to selectivity even though both were exposed. Neither position responded to MTSES− suggesting that these residues occupy either a size- or charge-restricted region of the pore. By contrast, MTSES− markedly increased, and MTSEA+ markedly decreased conductance of D1713C (D4) suggesting that the acidic side chain of Asp1713 acts electrostatically in an unrestricted region. These results suggest that Lys1418 lies in a restricted region favorable to cations, whereas Asp1713 is at a more peripheral location in the Na+ channel pore.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 1, 1997

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off