Figure 4.
Determination of protein abundances by mass spectrometry. Proteome analysis of strains containing p-PL-RybB-s8 and p-PL-RybB-s38 was performed in comparison to p-PL-RybB-wt and additional control strains in quadruplicates in the absence of oxacillin. Whisker plots show the median, minimum, and maximum of log2 intensities for the respective protein, while dots indicate individual measurements. OmpC is one of the native targets of RybB-wt and significantly reduced if RybB-wt is expressed. If the seed region is removed (RybB-Δseed) or altered (RybB-s8 and RybB-s38), this regulation is abrogated. While analyzing the data, a significant increase in LacZ was observed for constructs containing promoter PLlacO-1, which can be explained by LacI titration via the additional lac-operator sequences in the used PLlacO-1 promoter. The lac-repressor LacI shows no alteration in abundance supporting this hypothesis. RybB-s8 expression reduces the abundance of AcrA and AcrB. RybB-s38 expression does not reduce AcrA and AcrB abundances. One-way ANOVA with post-hoc Tukey HSD was applied for statistical testing. Significance levels indicate the comparison to empty plasmid pSL0009 (*: P < 0.05, **: P < 0.01, and ns: not significant).