Figure 3.

Several T6SS Components Are Subject to the Action of DsbA in S. marcescens Db10

(A) Recovery of P. fluorescens following co-culture with wild-type S. marcescens Db10 (WT), the ΔtssE and ΔdsbA1ΔdsbA2 mutants, and strains carrying chromosomally encoded C-terminal His₆ fusions with SMDB11_2251 (2251-His), TssM (TssM-His), or SMDB11_2269 (2269-His) in the parental or ΔdsbA1ΔdsbA2 mutant background. Individual data points are overlaid with mean ± SEM (n = 4).

(B) Mal-PEG labeling of free (reduced) cysteine residues in 2251-His in the parental (WT) or ΔdsbA1ΔdsbA2 mutant background. The 2251-His protein was detected by anti-His₆ immunoblot; two exposures of 2251-His in ΔdsbA1ΔdsbA2, with and without labeling, are shown to aid clarity. Non-tag indicates control strains without the 2251-His fusion.

(C) Immunoblot detection of TssM-His in membrane fractions from strains carrying the TssM-His fusion, in the parental or ΔdsbA1ΔdsbA2 background, and from these strains carrying either the vector control (+VC, pSUPROM) or a plasmid directing the expression of DsbA2 (+DsbA2, pSC1507) in trans. Bottom: immunoblot detection of the Cys-free control protein TssJ and the wild-type strain (WT) is a control with no fusion protein.

(D) As in (C), except that 2269-His and TssJ were detected in whole-cell samples of the strains indicated.

See also Figure S2.