The ESX System in Bacillus subtilis Mediates Protein Secretion
Figure 1
YukE is secreted, and secretion of YukE depends on other proteins encoded by the yuk/yue locus.
A: Schematic depicting the yuk/yue locus and surrounding genes. Currently, there are five annotated genes in the yuk operon: yukE, yukD, yukC, yukBA, and yueB [31], [32]. Recent high throughput transcriptomics data implicates yueC and/or yueD as potential members of the yuk/yue locus as well [33]. The predicted promoter (Pyuk) is indicated with an arrow. Homology to genes of other ESX/Ess systems is indicated below the corresponding yuk/yue gene name. B: Secretion assay for YukE. Cells were grown in LB medium to OD600nm of approximately 1.0–1.3. The cell pellet (P) was separated from the culture supernatant (S) by centrifugation. The pellet fractions were prepared into whole cell lysates and the supernatant fractions were filtered through a 0.2 micron filter and TCA precipitated. Samples were analyzed by SDS-PAGE under reducing conditions and immunoblot analysis with an α-YukE antibody and an α-SigmaA antibody as a loading/lysis control. The supernatants are shown in two exposures; the overexposed α-YukE blot (OE) allows visualization of faint bands. Data are representative of at least three biologically independent experiments. Pellet samples are equivalent to 0.1 OD and twenty-fold more was loaded for supernatant samples. Equivalent loading of precipitated supernatant samples was confirmed by densitometry of the Coomassie-stained gel.