Sandbox reserved 330: Difference between revisions
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== Toxin and Anti-toxin pair== | == Toxin and Anti-toxin pair== | ||
Addiction modules, consisting of a toxin and antitoxin pair, are controlled by operons which, are autoregulated at the transcriptional level. Bacteria rely on addiction modules to maintain plasmids within populations, and cells that do not inherit the plasmid encoded operon will not produce antixoin and will be inhibited by the toxin via post segregational killing. Once this operon is expressed, the bacterial strain is addicted to the antitoxin for survival. It is known that genomes of most bacteria have a toxin-antitoxin loci, which have been shown to be induced by stressful conditions. So thus, these modules play an important role in plasmid partitioning and cellular response to stress, where the maintenance of these modules prevents the lethal effect of toxin on cells | Addiction modules, consisting of a toxin and antitoxin pair, are controlled by operons which, are autoregulated at the transcriptional level. Bacteria rely on addiction modules to maintain plasmids within populations, and cells that do not inherit the plasmid encoded operon will not produce antixoin and will be inhibited by the toxin via post segregational killing. Once this operon is expressed, the bacterial strain is addicted to the antitoxin for survival. It is known that genomes of most bacteria have a toxin-antitoxin loci, which have been shown to be induced by stressful conditions. So thus, these modules play an important role in plasmid partitioning and cellular response to stress, where the maintenance of these modules prevents the lethal effect of toxin on cells. | ||
Previous studies of toxin families include MazF, ChpAK, and PemK, which all code for endoribonuclease that activates cellular mRNAs by cleaving them at specific sites. Recently, there is a Bacilis subtilis gene product discovered, EndoA, that is a member of RNAses, which is likely the gene product of the YdcE gene. This EndoA has similar cleavage pattern specificity as MazF and PemK, with cleavage products of a 3’phosphate and 5’OH group. Further study revealed that a coexpression of an upstream gene, YdcD reverses the effects of this particular toxin, and thus, this is the first antitoxin-toxin system of Bacilis subtilis. | Previous studies of toxin families include MazF, ChpAK, and PemK, which all code for endoribonuclease that activates cellular mRNAs by cleaving them at specific sites. Recently, there is a Bacilis subtilis gene product discovered, EndoA, that is a member of RNAses, which is likely the gene product of the YdcE gene. This EndoA has similar cleavage pattern specificity as MazF and PemK, with cleavage products of a 3’phosphate and 5’OH group. Further study revealed that a coexpression of an upstream gene, YdcD reverses the effects of this particular toxin, and thus, this is the first antitoxin-toxin system of Bacilis subtilis. | ||
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==Tautomerase Superfamily== | ==Tautomerase Superfamily== | ||
The YdcE protein(EndoA) has been categorized as part of a subfamily of the tautomerase superfamily, which includes the 4-oxalocrotonate tautomerase. This superfamily is composed of structurally homologous proteins that are constructed from a simple β-α-β fold. These homologous proteins share a key mechanistic feature of using an amino terminal proline, which has an unsually low pKa, as a general base in a keto-enol tautomerization. | The YdcE protein(EndoA) has been categorized as part of a subfamily of the tautomerase superfamily, which includes the 4-oxalocrotonate tautomerase. This superfamily is composed of structurally homologous proteins that are constructed from a simple β-α-β fold. These homologous proteins share a key mechanistic feature of using an amino terminal proline, which has an unsually low pKa, as a general base in a keto-enol tautomerization<ref > Almrud, J.J., Kern, A.D., Wang, S.C., Czerwinski, R.M., Johnson, W.H., Murzin, A.G., Hackert, M.L., Whitman, C.P. The crystal structure of YdcE, a 4-oxalocrotonate tautomerase homologue from Escherichia coli., confirms the structural basis for oligomer diversity. Biochemistry.2002. August;41(40):12010-12024</ref>. | ||
==Structure== | ==Structure== | ||
