Functional dissection of the putative translocon protein SseD. Predictions of transmembrane domains (A) and coiled-coil regions (B) in SseD were performed as described for Fig. 1. Four transmembrane regions and one coiled-coil region were predicted for SseD using TMpred and COILS. The chaperone binding site for SseA is located within the C-terminus of SseD . C) The location of TM and coiled-coil regions in wild-type SseD is indicated and the positions of internal deletions are indicated by arrows. N- or C-terminal truncations are indicated by vertical red lines. Plasmid-borne mutant alleles were also integrated into the chromosome applying λ. Red recombineering recombined with positive selection . D) Analyses of synthesis and secretion of SseD variants under in vitro conditions. For the in vitro studies, bacteria harboring wild-type SseD, chromosomal or plasmid-borne deletion variants of SseD were analyzed as described in Fig. 2. Secreted proteins were detached from the cell surface or directly recovered from the supernatant by precipitation with TCA and subjected to Western blot analyses using antiserum raised against SseD. The presents or absence of SseD in the bacterial lysate or secreted fractions (detached fraction or supernatant) is indicated as + or -. The analyses of synthesis and secretion of plasmid-encoded variants of SseD are shown in Additional file 2.