We all knew that antitoxins are highly specific for their associated toxins and cross-talk is similarly unlikely to occur in vivo (Ramage et al. 2009).
However, if a toxin deletion mutant was constructed, where will the antitoxin bind to if there isn't any toxin?
Will the antitoxin bind to the DNA and affect its replication since an antitoxin have a DNA binding domain?
Many thanks in advance!
If the binding of the antitoxin to DNA was deleterious, mutants would soon appear where the respective antitoxin-encoding gene would be altered to either prevent its binding to DNA or prevent its expression (e. g. by a stop codon early in the gene or mutating the promoter). On the other hand, if the binding of the antitoxin to the DNA was not deleterious, the cell may be forced to keep the gene, especially if wt cells harboring the toxin are still around.
Thank you Mr Libor!
Does Mr Libor means that the toxin deleted mutant will still be resolved with some alterations in antitoxin gene if the binding was deleterious (and the colony will still be seen on the plate) ?
This is because I am facing the problem when I try to construct the toxin gene deletion mutant using the homologous recombination and allele replacement method. However, I cannot get the mutant after quite a numbers of resolved merodiploids screened.
All my resolved merodiploids were found to be the wt cells. Hence, I am suspecting that toxin-gene-deleted mutant was successfully resolved. However, it is the antitoxin binds toward the DNA of the deleted mutant and inhibits its DNA replication. Hence, I cannot get the deleted mutant colony on my plate.
It is just some of my deduction and reasoning, but, is it possible to be true?
Yes, it is possible. Have your tried to delete the complete TA system (both genes) ? If that worked, it would strongly indicate that the antitoxin may in fact function as a toxin itself, when without its partner!
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