Construction of a Genetic Toggle Switch in Escherichia coli

All diagrams except the for the detailed switch diagram taken from:

Gardner, T.S., Cantor, C.R. and Collins, J.J. (2000)Construction of a Genetic Toggle Switch in

Escherichia coli Nature 403 (6767) 339-343

Design

U = concentration repressor 1

V = concentration repressor 2

α = effective rates of synthesis

β and γ = cooperativity of repressors

udtdu

1

1

vudt

dv

1

2

Detail

Specifications

In absence of inducer,

only one promoter

should be effectively

active

Addition of inducer (eg.

IPTG or thermal pulse)

should trigger switching

to desired state

Product

3 Promotersystems:

Low State:

PLs1con (CI) (Stronger)

PLtetO-1 (TetR)

High State:

Ptrc-2 (LacI)

v

u

Characteristics

η = cooperativity of IPTG binding

K = dissociation constant

vKIPTG

u

dt

dv

))

)/][1((1/(2

Pros Cons .

• Is completely stable in both states

• Can be switched between states easily

• Small construct so products can be placed downstream

• Requires protein degradation so takes a LONG time to switch between states

• IPTG cannot be removed from environment after induction