Escherichia coli Preprotein Translocase

Polar molecules cross lipid-based membranes through proteinaceous transport systems. Sugars, amino acids, and small ions are recognized by transporters of great specificity and then transferred along (still ill defined) paths within the transporter and released on the opposite membrane side. Subcellular compartmentation entails the selective transport of newly made preproteins across membranes. Since preproteins are of varied sequence and can be as large as their transporter, it was likely that their transporter would have unique mechanistic features.