OmpF-Lpp signal sequence mutants with varying charge hydrophobicity ratios provide evidence for a phosphatidylglycerol-signal sequence interaction during protein translocation across the Escherichia coli inner membrane

Using inverted Escherichia coli inner membrane vesicles we have analyzed the phosphatidylglycerol dependence of translocation of an OmpF-Lpp fusion protein carrying a signal sequence with varying positive charge at the N terminus and a hydrophobic core of varying length. It is shown that there is a direct relationship between the phosphatidylglycerol requirement of translocation and the requirement within the translocation process for positive charges on the signal sequence. This provides further evidence that the negative head group of the lipid is required for functional interaction with the positively charged N terminus of the signal sequence.