This is a composite part which contains a T7 promoter, RBS, lac operator, 6x his tag, and YoeB. YoeB is the toxin in the YefM/YoeB toxin-antitoxin pair from E. coli.
Usage and Biology
Within the E.coli genome, there is the naturally occurring toxin-antitoxin system whose production is altered in response to various types of stress. In layman’s terms, a toxin-antitoxin system consists of two genes: one coding for the toxin, or “poison”, and one coding for the antitoxin, or “antidote”.
There are three different types of toxin/antitoxin systems, all with different products effectively committing apoptosis. A general overview of all types are listed below.
Type 1: Inhibition takes place when the antitoxin RNA binds to the complementary toxin mRNA. If there is not enough antitoxin RNA being transcribed, toxin proteins will be produced, inducing toxicity through cell membrane damage. Toxin RNA has a half life of ~20 minutes, while antitoxin RNA has a half life of ~30 seconds.
Type 2: both genes code for separate proteins, which bind to each other in a normal, unstressed state. While undergoing stressful conditions, the production of antitoxins will drastically decrease, allowing the toxin protein to act as a pseudo-RNAase, cleaving mRNA.
Type 3: The most recently discovered, inhibition of this toxin requires the interplay between a toxin protein and an antitoxin RNA gene. There is only one example of this system so far - the ToxIN system from the bacterial plant pathogen Erwinia carotovora.
YoeB is a Type 2 toxin. For the purposes of the 2012 UCSF iGEM team, (tuning population ratios of symbiotic strains), Type 2 systems were determined to be ideal, since they have the greatest chance of longevity/sustainability as proteins, rather than RNA strands.
