Brown

From 2007.igem.org

Welcome to our World

[http://www.brownigem.com The Website: Our Public Image]

[http://openwetware.org/wiki/IGEM:Brown/2007 The Resource: Our Calculations]

Projects

Tri-stable Toggle Switch

The Tri-stable Toggle Switch will be able to produce three distinct, continuous (stable) outputs for each of the three inputs. A chemical will induce the system to "lock into" one state while repressing the other two states. Our three constructs are pBAD->LacI->TetR, pLacI->AraC->TetR, and pTet->AraC->LacI, where AraC represses pBAD, LacI represses pLac and [http://en.wikipedia.org/wiki/TetR TetR] represses pTet. The three chemicals ([http://en.wikipedia.org/wiki/Arabinose arabinose], [http://en.wikipedia.org/wiki/IPTG IPTG] and [http://en.wikipedia.org/wiki/Tetracycline Tetracycline], respectively), cause conformational changes in their respective repressor proteins which leads to gene expression. For example, in the presence of arabinose, AraC cannot repress pBAD so LacI and TetR are produced which in turn repress pTet and pLac.

The architecture of our system is as follows:

The Tri-stable Toggle Switch Architecture

AraC/BAD

The gene AraC one of several genes (AraA, AraB, AraD, etc) originally for the metabolism of arabinose.[http://www.mun.ca/biochem/courses/3107/Topics/Ara_operon.html] The protein forms a dimer in with and without arabinose but the structural change activates or represses the pBAD ([http://en.wikipedia.org/wiki/Bcl-2-associated_death_promoter Bcl-2-associated death promoter], an apoptotic regulator in humans).

Dimer structure with arabinose on the left (yellow)

The left image shows the araC dimer repressing transcription, while the right conformation enables transcription

LacI

TetR