Fig. 1

S. Typhi produces two distinct typhoid toxins with common active but different delivery subunits. a Illustration of the S. Typhi typhoid toxin genomic locus, as well as a distant locus that encodes pltC (sty1364), an orphan pertussis-like toxin delivery subunit that exhibits homology to pltB. b, and c Expression of pltC, pltB and cdtB over time under conditions that stimulate typhoid toxin gene expression. The β-galactosidase activity in the pltC:lacZ, pltB:lacZ and cdtB:lacZ S. Typhi reporter strains was measured at the indicated time points following infection of Henle-407 cells b or growth in TTIM medium c. Values indicate the mean ±S.D. for three independent samples. d Interaction of PltC with PltA/CdtB in S. Typhi grown in TTIM. Cell lysates from S. Typhi strains encoding cdtB-3xFLAG, pltC-3xFLAG, cdtB-3xFLAG (in ΔpltA background), or malE-3xFLAG were immunoprecipitated with an anti-FLAG antibody and interacting proteins were identified using LC/MS/MS. For each sample the number of peptides for the five most abundant proteins recovered and for all typhoid toxin subunits (color-coded according to panel a) are shown. *Detection of PltB with the LC–MS/MS protocol even for purified typhoid toxin preparations is inefficient. e S. Typhi produces both PltB- and PltC-typhoid toxins within infected human cells. Henle-407 cells were infected with S. Typhi wild type or the indicated mutant strains encoding 3xFLAG epitope-tagged CdtB or PltC (as indicated) and 24 hs post-infection the interaction of the indicated toxin components were probed by co-immunoprecipitation and western blot analysis. f PltB forms a complex with CdtB, but not with PltC. The interaction of the indicated toxin components in cell lysates of the indicated strains encoding 3xFLAG epitope tagged CdtB or PltC were probed by anti-FLAG co-immunoprecipitation and western blot analysis. Whole cell lysates (Pre IP) and immunoprecipitated samples (post IP) were probed using an anti-FLAG antibody as a control (top blot) and an anti-PltB antibody (bottom blot) to identify PltB interactions with CdtB or PltC in the indicated strains. Ig. l. c.: Immunoglobulin light chain detected by the secondary antibody. Source data are provided as a Source Data file