Model of the gal system in E. coli. A: View of the gal system in E. coli. The activator CRP activates both galETK and GalS. GalS inhibits galETK and negatively auto-regulates itself. GalSinh, which is a shortcut representing both β-D-galactose and D-fucose, cancels the inhibitory effect of GalsS on galETK. B: Evolution of the level of galETK when CRP is activated at time t = 0. The level are represented using relative values with respect to the stable state galETKSt. The situation in which no GalSinh is not expressed is represented in blue. This corresponds to an I1-FFL. The situation in which GalSinh is present is represented in red. In this situation, the model behaves like with a simple activation. The response time, measured as the time needed to reach galETKSt/2 is shorter in the absence of GalSinh.
Schaub et al. BMC Systems Biology 2007 1:4 doi:10.1186/1752-0509-1-4