LIPID AND PEPTIDE SPECIFICITIES IN SIGNAL PEPTIDE LIPID INTERACTIONS IN MODEL MEMBRANES

The present data show the critical importance of the anionic lipid content in monomolecular layers for the interaction with PhoE signal peptide. At 37°C and 100 mM NaCl the interaction is maximal at 30-40 mol% anionic lipid. The results correlate with the reduced translocation competence of Escherichia coli strain HD3122, which has a much lower anionic lipid content as compared to the wild- type strain SD12 (De Vrije et al. (1988) Nature 334, 173-175). PhoE signal peptide analogs as N-formyl PhoE signal peptide, PhoE signal peptide +(1-7) and PhoE signal peptide Val-8 → Trp-8 show the same lipid preference as PhoE signal peptide. On the other hand the affinity for an anionic lipid interface is strongly reduced for PhoE signal peptide Lys-19,-20 → Asp-19,-20, which correlates with the less efficient translocation of PhoE protein carrying this signal sequence. At limiting anionic lipid concentrations there is a temperature and salt effect on the observed interaction, which is related to a conformational change of the peptide. Signal sequences show clearly conformational flexibility in responds to environmental conditions. Under the conditions used in this study FTIR spectra of PhoE signal peptide-DOPG monolayers show a high content of β-structure and β-turn. © 1990.