Fig 5.

Effects of RegR on the expression of secreted and surface-associated proteins. RegR⁺ [E22 ΔregR(pYS3)] and RegR⁻ (E22 ΔregR) strains of E22 were grown in DMEM (for secretome analysis) or in Luria broth in the absence or presence of 45 mM bicarbonate (for analysis of heat-extracted fractions). Proteins were separated by SDS-PAGE and stained with Coomassie brilliant blue R250. Four protein bands (two from the secretome fractions and two from the heat-extracted fractions) which were present in the RegR⁺ but not in the RegR⁻ strain (indicated by asterisks) were excised and analyzed by tandem mass spectrometry. In the heat-extracted fractions, two bands which are abundant in the absence of bicarbonate (boxed) were analyzed by tandem mass spectrometry. The identities of these proteins are shown at the right of the gels.