Diphtheria Toxin Forms Pores of Different Sizes Depending on Its Concentration in Membranes: Probable Relationship to Oligomerization

Diphtheria Toxin Forms Pores of Different Sizes Depending on Its Concentration in Membranes:... Diphtheria toxin forms pores in biological and model membranes upon exposure to low pH. These pores may play a critical role in the translocation of the A chain of the toxin into the cytoplasm. The effect of protein concentration on diphtheria toxin pore formation in model membrane systems was assayed by using a new fluorescence quenching method. In this method, the movement of Cascade Blue labeled dextrans of various sizes across membranes is detected by antibodies which quench Cascade Blue fluorescence. It was found that at low pH the toxin makes pores in phosphatidylcholine/phosphatidylglycerol vesicles with a size that depends on protein concentration. At the lowest toxin concentrations only the entrapped free fluorophore (MW 538) could be released from model membranes. At intermediate toxin concentrations, a 3 kD dextran could be released. At the highest toxin concentration, a 10 kD dextran could be released, but not a 70 kD dextran. Similar pore properties were found using vesicles lacking phosphatidylglycerol or containing 30% cholesterol. However, larger pores formed at lower protein concentrations in the presence of cholesterol. The dependence of pore size on toxin concentration suggests that toxin oligomerization regulates pore size. This behavior may explain some of the conflicting data on the size of the pores formed by diphtheria toxin. The formation of oligomers by membrane-inserted toxin is consistent with the results of chemical crosslinking and measurements of the self-quenching of rhodamine-labeled toxin. Based on these experiments we propose diphtheria toxin forms oligomers with a variable stoichiometry, and that pore size depends on the oligomerization state. Reasons why oligomerization could assist proper membrane insertion of the toxin and other proteins that convert from soluble to membrane-inserted states are discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Diphtheria Toxin Forms Pores of Different Sizes Depending on Its Concentration in Membranes: Probable Relationship to Oligomerization

Loading next page...
Copyright © Inc. by 1999 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