Figure 4. A proposed reciprocating piston model of the preprotein secretion pathway in bacteria.
Steps 1–4: Initiation of protein translocation is commenced by SecA cytoplasmic homodimer (1) and ends with the release of SecB chaperone (4). Steps 5–9: The translocation cycle is initiated with the release of SecA protomer (5) which is recycled back into the translocation cycle (6–7), finally culminating in the release of preprotein into the periplasm (9).
Reproduced with permission from [46] © Springer (2011).