B) For analyses of SseB secretion GDC-0449 and translocon formation lysozyme treatment was omitted. Note the labeling of SseB in the bacterial cytoplasm for all strain except

for the sseB strain in A) and the absence or rare occurrence of punctuated surface labeling for all strains except WT and sseB [psseB] in B). Deletional analyses of SseD We applied a similar deletion strategy to SseD. Based on the predictions of transmembrane regions (Fig. 6A; see also Additional file 2) and coiled-coil domains (Fig. 6B), variants of SseD were generated that lacked hydrophobic, putative TM domains, the coiled-coil domain, the chaperone-binding site or the N- or C-terminal parts of the protein (Fig. 6C). In addition to episomal expression of mutated sseD, exchange of the WT allele of sseD in the chromosome of Salmonella against mutant alleles was this website performed. The synthesis of SseDΔC1, SseDΔC2 and SseDΔC3 was observed if expressed by episomal genes, but not in strains with chromosomal deletions, likely due to lower expression levels. Synthesis of SseDΔN1, SseDΔ1 and SseDCΔ4 was

not detectable at all. We observed that the larger number of the deletion constructs was not secreted under in vitro conditions (Fig. 6D, Suppl. Fig. 1). Secretion was only detected for the constructs SseDΔ3 and SseDΔ4 that lacked hydrophobic domains in the central region of Protein kinase N1 the protein. The presence of the mutant alleles on episomal elements or in the chromosome had no effect on the efficiency of secretion. We have not been able to detect surface structures containing SseD for WT or mutant strains using the antiserum against SseD (data not shown). These observations show that the integrity of the primary sequence of SseD is of critical importance for the secretion of the protein and more sensitive to alterations compared to SseB. Figure 6 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 [10]. 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 [29]. 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.