Team:Tianjin/Model
Heterogenous Degradation By PETase
Model Overview
R-R system (namely reporting and regulation system), is used in our project in order to make the expression of PET degrading enzyme visible and regular. As its name implies, this system consists of two independent part, reporting and regulation. We test our reporting part in E.coli and regulation part in Saccharomyces cerevisiae .
1. Reporting System
The basis of our reporting system is the part BBa_K339007, Designed by Emily Hicks from Group iGEM10_Calgary. This part can sense the CpxR protein, which will form spontaneously in E.coli when inclusion body and misfolding protein present in the periplasm of E.coli, and then start expressing RFP so that we can detect red fluorescence. As we all know, the inclusion body will inevitably form when we overexpress heterologous protein like PETase in E.coli. Therefore, the emission of red fluorescence can report the overexpression of PETase. What is more, this device can be modified to report overexpression of any heterologous protein only if the PETase gene is replaced by another heterologous gene. After the red fluorescence is detected, we could start the purification of protein.
2. Cell Lysis Based Regulation System
The regulation system consists of two section. The first section is based on the already mentioned reporting system. We change the RFP gene to the novel ddpX (D-alanyl-D-alanine dipeptidase) gene from E.coli genome. The ddpX gene can hydrolyze the D-Ala-D-Ala structure in peptidoglycan molecule and cause damage to the cell wall of E.coli. Under normal condition, this gene only express when the cell is in starvation mode in order to use hydrolysate alanine as carbon source. However, if we overexpress this gene, the cell wall will be dissolved and finally cell lysis will happen. Therefore, in this system, when the PETase is overexpressed, the spontaneously forming inclusion body will induce the expression of ddpX and cause cell lysis. It will provide us with a novel and convenient and way of protein purification when you use E.coli as chassis.
