FIGURE 6.

Working model for proOmpA translocation. A, WT SecA, SecG with its topology, and (pro)OmpA (waved line) are shown. T and D represent ATP and ADP, respectively. At step 0, cleavage of the signal sequence is shown. The extent of translocation (steps 1–5 and 1′) is reflected by intermediate species (I₁₆, I₁₈, I₂₆, and I₂₈). B, model for the reaction involving D209N SecA. The mutant and wild-type SecA are indicated as 209 and WT. For details, see “Discussion.”