FIGURE 4.

The Sec translocase is required to translocate the Pf3 tail or the F₀a N-tail with a positively charged residue. E. coli CM124 cells bearing different plasmids were radiolabeled and analyzed by the protease accessibility assay, as described in the legend to Fig. 2. The plasmids expressed Pf3-LepTM V4E, V15D, V4R, V15R, V15K, V4E/V15D, or V4R/V15R; a-LepTM, a-LepTM R24D or R24A; or a-aTM, a-aTM R24D or R24A. Representative OmpA data for the protease-mapping study is shown at the bottom.