From 2007.igem.org

Saint-Petersburg iGem2007 team

This year our team is participating for the first time in iGem2007 project.

Our team works at the Saint-Petersburg State Polytechnical University in the department of Biophysics.

About Us

• Students:
  • Tatiana Moiseeva
  • Alexey Shalygin
  • Maria Ditina
  • Gennady Zakharov

• Our Instructors:
  • Evgeny Zatulovskiy
  • Vasiliy Romanov
  • Alexej Skvortsov

Our Project

General

The aim of our project is to build on the E.Coli bacteria the copper sensor. To solve this problem we need to use the copper-homeostasis system of E.Coli. The most convenient for our purposes protein is CusR, the component of the Copper-Responsive Two-Component System.

We intend to use the CusR promoter with the reporter gene to build sensor.

Problem

The main problem of our project is to make the "trigger" response with the two stable levels (high copper сoncentration/high copper сoncentration). Constructing such switch is a challenge.

So we perform a theoretical study of this problem.

So, if we want to use only proteins without secondary metabolites, the best trigger sheme is the next:

In this scheme we can observe the switching between two repressors (x and y), depending on the transcription level from the copper-depended promoter.

But this scheme is rather difficult and need many constructing operations. So, we decided to think more simple scheme, using the secondary metabolites.

Scheme with secondary metabolites

Firsly, to use the secondary metabolites, we need to have metabolite-depended activator or repressor. Such biobrick avaliable in the iGem2007 registry as part BBa_C0062, the LuxR protein. In complex with HSL (homoserine lactone), LuxR binds to the Lux promoter, activating transcription from part BBa_R0062.

Secondary, we need a HSL-syntase. Probably, it may be part BBa_C0061, the enzyme for creating acyl-homoserine lactones from normal cell metabolites. If we have this enzyme after the copper-depended promoter, we can synthesize HSL in response to increasing copper level, and start transcription of LuxR promoter.

In this scheme we can significantly increase signal level without making the triggers. For my mind, this sheme is optimal, certainly if this biobriks are working.