FIG 1.

TcpP forms intramolecular and intermolecular disulfide bonds. Lysates of V. cholerae (EK459 ΔtoxR ΔtcpP) expressing pMMB-TcpP-HSV and either pSK or pSK-ToxR-HA (a ToxR-expressing plasmid with a C-terminal HA tag) were incubated with iodoacetamide prior to resuspension in sample buffer with or without DTT. Blots were probed with anti-HSV primary antibody and alkaline phosphatase-conjugated anti-mouse secondary antibody. Mutations in either or both periplasmic cysteines were used to perturb disulfide bond formation. The arrows and diagrams along the side of the blot indicate the state of the periplasmic cysteines in each form of TcpP detected.