Fig. 4.

Analysis of enriched fractions isolated from null mutant strains lacking indicated component protein(s). (A) Fractions isolated from designated L. pneumophila strains were analyzed by SDS–polyacrylamide gels. Core components DotC, DotD, DotH, DotF, and DotG were detected by Western immunoblotting using specific antibodies against indicated core component proteins. MOMP was detected by silver staining and used as an internal control for isolation yield. (B–F) Ring structures visualized by transmission electron microscopy analysis isolated from (B) wild-type, (C) ΔdotG, (D and E) ΔdotF, and (F) ΔdotF ΔdotG strains. In B–D and F, small and large white arrows denote the wild-type and the ΔdotG-type ring structures with small and large pores, respectively. In E, two distinct kinds of complexes isolated from the ΔdotF strain are shown. (G) Schematic cartoons illustrating the observed ring structures isolated from wild-type, ΔdotG, and ΔdotF strains. Internal and external diameters of the complexes are presented as the mean ± SEM. Asterisks denote significant difference (P < 0.001) by z-test or Student t test. ns, not significant.