Reactivity of Cysteines in the Transmembrane Region of the Na,K-ATPase α Subunit Probed with Hg2+

Reactivity of Cysteines in the Transmembrane Region of the Na,K-ATPase α Subunit Probed with Hg2+ To gain insight into the structure and conformational coupling in the Na,K-ATPase, this study characterized the reaction of the α1 subunit transmembrane cysteines with a small probe. Intact HeLa cells expressing heterologous Na,K-ATPase were treated with (μm) HgCl2 after placing the enzyme predominantly in either of two conformations, phosphorylated E2P.Na/E2P or dephosphorylated ATP.E1.K/ATP.E1. Under both conditions the treatment led to enzyme inactivation following a double exponential kinetic as determined by ouabain-sensitive K+ uptake measurements. However, the rate constant of the slow reacting component was ten times larger when the protein was probed in a medium that would favor enzyme phosphorylation. Enzymes carrying mutations of cysteines located in the α1 subunit transmembrane region were used to identify the reacting–SH groups. Replacement Cys104Ser reduced enzyme inactivation by removing the slow reacting component under both treatment conditions. Replacement of Cys964 reduced the inactivation rate constant of the fast reacting component (79%) and removed the slow reacting component when the dephosphorylated enzyme was treated with Hg2+. Moreover, Cys964Ser substituted enzyme was insensitive to Hg2+ when treated under phosphorylation conditions. These results indicate that Cys964 is involved in the fast inactivation by Hg2+. Although the double mutant Cys964, 104Ser was still partially inactivated by treatment under nonphosphorylating conditions, an enzyme devoid of transmembrane cysteines was insensitive to Hg2+ under all treatment conditions. Thus, this enzyme provides a background where accessibility of engineered transmembrane cysteines can be tested. The Journal of Membrane Biology Springer Journals

Reactivity of Cysteines in the Transmembrane Region of the Na,K-ATPase α Subunit Probed with Hg2+

Loading next page...
Copyright © Inc. by 2000 Springer-Verlag New York
Life Sciences; Biochemistry, general; Human Physiology
Publisher site
See Article on Publisher Site

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 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

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

Monthly Plan

  • Read unlimited articles
  • Personalized recommendations
  • No expiration
  • Print 20 pages per month
  • 20% off on PDF purchases
  • Organize your research
  • Get updates on your journals and topic searches


Start Free Trial

14-day Free Trial

Best Deal — 39% off

Annual Plan

  • All the features of the Professional Plan, but for 39% off!
  • Billed annually
  • No expiration
  • For the normal price of 10 articles elsewhere, you get one full year of unlimited access to articles.



billed annually
Start Free Trial

14-day Free Trial