CH391L/S12/ToxinAntitoxins: Difference between revisions
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= | =Metabolism Based Plasmid Addiction= | ||
= | =Operator Repressor Titration Systems= | ||
Revision as of 12:57, 17 February 2012
Toxin-Antitoxins
Basics of Toxin-Antitoxin (TA) Systems
TA systems are gene addiction constructs that occur naturally in prokaryotes, eukaryotes, and archaea. They consist of two coexpressed proteins: a stable toxin and a labile antitoxin that inhibits the detrimental effects of the toxin on the cell. If expression of the TA gene cassette is inhibited or the genes are purged from cell (from losing a plasmid carrying the TA genes, for example), the labile antitoxin in the cell degrades faster than the stable toxin. The newly uninhibited toxin then exerts its affect on the cell, resulting in growth inhibition or cell death. TA systems work by a wide variety of mechanisms, delineated into three major classes based on the interaction of toxin and antitoxin.
Type I Systems
In Type I systems, regulation of the toxin occurs on the RNA level. Antitoxins in this class are antisense RNA that repress the translation of the toxin by binding to its mRNA transcript.
Type II Systems
In Type II Systems, antitoxin proteins bind to and inhibit toxin proteins.
Type III Systems
With only one example recently characterized, type III systems work by a small RNA antitoxin directly binding to and inhibiting the protein toxin.
