Fig. 1.

EscL, EscN, and EscQ are essential for type III secretion in EPEC. (A) Protein secretion profiles of the EPEC WT, ΔescL, ΔescN, and ΔescQ strains as well as the null mutants complemented with a double-HA-tagged version of the missing protein (pEscL-2HA, pEscN-2HA, or pEscQ-2HA). Secreted proteins were concentrated from supernatants of bacterial cultures grown in DMEM and analyzed by SDS–12.5% PAGE and Coomassie staining. The locations of the translocators EspA, EspB, and EspD are indicated at the left of the gel. The location of EPEC EspC, which is not secreted via the LEE-encoded T3SS, is also indicated. (B) Protein secretion profiles of EPEC double-deletion strains complemented with the two missing proteins. Secreted proteins were processed as described for panel A.