Fig. 3.

Hierarchy in the recruitment to the needle complex of export apparatus components. Protein complexes of purified inner membrane fractions of wild type (wt) and the indicated mutants of S. Typhimurium expressing FLAG-epitope tagged InvA or SpaP were solubilized with DDM, separated by BN-PAGE, and analyzed by Western blotting using antibodies directed to the NC base or FLAG (to detect either SpaP or InvA; A). The intensity of the bands corresponding to SpaP or InvA associated with the NC was quantified as above (B), and values represent the mean ± SD of three independent experiments. Values were standardized relative to the levels of the NC and across different samples relative to wild type, which was assigned an arbitrary value of 1. The total levels of SpaP-FLAG and InvA-FLAG in the different mutants are shown in Fig. 2B.