Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 35, Pages 12537-12542Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0500558102
Keywords
Listeria; toxin; pore
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Funding
- NIAID NIH HHS [R01AI037657, R01 AI037657] Funding Source: Medline
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Listeriolysin O (LLO) is a cholesterol-dependent cytolysin that is an essential virulence factor of Listeria monocytogenes. LLO poreforming activity is pH-dependent; it is active at acidic pH (< 6), but not at neutral pH. In contrast to other pH-dependent toxins, we have determined that LLO pore-forming activity is controlled by a rapid and irreversible denaturation of its structure at neutral pH at temperatures > 30 degrees C. Rapid denaturation is triggered at neutral pH by the premature unfolding of the domain 3 transmembrane beta-hairpins; structures that normally form the transmembrane beta-barrel. A triad of acidic residues within domain 3 function as the pH sensor and initiate the denaturation of LLO by destabilizing the structure of domain 3. These studies provide a view of a molecular mechanism by which the activity of a bacterial toxin is regulated by pH.
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