Figure 2

Two distinct parameter value sets. (a) Posterior distributions for the protein synthesis rates for KorB and KorA (see Figure. 3) are bimodal. (b) KorB concentrations from model simulations using typical parameter values from the left peak for: dimers in wild type (purple); monomers in wild type (red); total monomers in wild type (black); and total monomers in the plasmid mutant (cyan). The latter three curves are indistinguishable and have been superimposed with dashed lines. For these parameter values, KorB is mainly present as monomers; the same is true for KorA (data not shown). Although the experimentally measured concentration of KorB increased in the mutant strain, the steady state concentrations from these simulations are within the 50% experimental error associated with Western blot analysis. (c) KorB concentrations from model simulations using typical parameter values from the right peak. KorB is mainly present as dimers; the same is true for KorA (data not shown). (d) Proportions of DNA occupation by KorA or KorB dimers in steady state, with left peak parameter values, for empty DNA (D), KorA-DNA complex (X), KorB-DNA complex (Y) and KorA-KorB-DNA complex (Z). The DNA is mostly unoccupied, allowing full transcription to take place, although the presence of a low concentration of KorA dimers indicates some partial repression by KorA. The promoter is very rarely occupied by KorB dimers. (e) Proportions of DNA occupation for right peak parameter values. The promoter is generally repressed, being occupied by both KorA and KorB dimers, and transcription from the unoccupied state is rare.