The inability of DevRC to support full induction is attributed, at least in part, to a failure to cooperatively recruit DevR to adjacently-placed secondary binding sites.
This result indicates that the nit-6 promoter is extremely sensitive to nitrate, with full induction of mRNA at 0.5 mM.
Yet, only a subset of cells of the enriched populations (25% for MOV-scT6 and 44% for MOV-scT6cA, respectively) exhibited induction at 30 ng/ml Dox, while full induction could be achieved at maximum effector rates, 1000 ng/ml Dox (>95%).
> -wrap-foot> The relative decrease is calculated as the maximal amount of isoprene at full induction devided by the maximal amount of isoprene at limited induction (dashes indicate that measurement did not apply here; explained in detail in the text, with numbering of the respective enzymatic steps).
From our data, it is clear that Darunavir and Atazanavir had the strongest inhibitory effects on PR activity, resulting in eGFP expression at just 1nM, while IDV and Tipranavir, showed the weakest inhibitory effects, nevertheless achieving full induction of eGFP expression at about 5µM.
At full induction ([IPTG] > 200 μM), this cost to lac operon expression results in a reduction in growth rate of about 0.2 doublings per hour.
In their study, populations transduced by the autoregulated vector displayed a nearly full induction of gene expression at yet intermediate effector (Dox) concentrations and an increase in positive cells at higher Dox concentration.
It should be pointed out again here that overexpression of all mutants resulted in a more or less severe drop in mtDNA levels, while no such drop was observed for the wild-type protein even at full induction.
In contrast, full induction rates were observed at already lower effector concentrations for the autoregulated MOV-scT6cA vector and further increase in effector (Dox) concentration resulted only in increased numbers of induced cells.
While this may suggest that the low-affinity transporter is poorly induced for our parameter set, the low-affinity transporter alone could mediate full induction of the pathway at high extracellular sugar concentrations (SI Figure S4).
