Team:Imperial College London/Drylab/Protein Production

Protein Production

Based on the Genetic circuit, a LacI-IPTG inducible promoter is responsible for kickstarting the production of the drug.

• In the absence of IPTG, LacI represses the production of the drug (Cellulase or PAH)
• When IPTG is introduced, the LacI repressing pathway is “de-repressed”, and some output protein is produced.

Our goals

The modelling aims to provide an overview and better understanding of the M1 system’s function by:

• Characterizing the system.
• Modeling to account for several factors that may reduce/hinder the production of the protein drug such as:
  • Lac promoter leakiness
  • IPTG toxicity
  • Stability of output protein

This module is an integral part of the design, as large-scale commercialization of the drug of interest depends on finding the optimal conditions for protein production.

  about the model assumptions and predictions!

The System

There are 6 differential equations that describe the behaviour of this system.
  about the equations and what they mean!

Summary of simulation results

• When we introduce IPTG into the system, it temporarily removes LacI from the system. Hence, during this period of time, we produce the drug of interest.
• When the effects of IPTG wear off, the system returns to equilibrium.
• The more IPTG we add in, the higher the amount of output protein.

  about the simulations!

• The effects of IPTG toxicity were investigated and we found that for these concentration ranges, IPTG is not toxic to cells. See the pdf of results for further details:Media:II09_IPTG_growth.ogg
• The constants in this model are arbitrary. We justify our usage of these values with a more detailed dynamical analysis of the system, which shows that it can only have fixed points[ref Strogatz]. Media:II09_Prot_stability analysis.ogg

Conclusion

• The greater the strength of the Lac promoter, the greater the repressive action of LacI prior IPTG induction.
• The greater the Lac promoter leakiness (k_{leak) the greater the basal amount of expression of protein of interest, prior IPTG induction.}
• The greater the amount of IPTG introduced, the greater the size of the bump in production of protein of interest.
• Here we assumed that the range of IPTG we have introduced is non-toxic for our cells. Growth curves will tell us whether IPTG does limit cell growth at the ranges we are interested in.