Procaine, a Local Anesthetic Interacting with the Cell Membrane, Inhibits the Processing of Precursor Forms of Periplasmic Proteins in Escherichia coli

Abstract

Treatment of E. coli cells with procaine (0.55%, wt/vol) results in the accumulation of precursor in addition to mature forms of 2 periplasmic proteins, alkaline phosphatase and glutamine-binding protein. The precursor form of alkaline phosphatase has a higher MW than the mature form by about 2600. An experimental technique is described to isolate and purify precursor forms of any presumably exported protein. After the membrane solubilization step in the presence of nonionic detergent, a peptidase is stimulated, resulting in partial cleavage of the precursors. The products of this cleavage were identified as the mature protein and presumably the signal peptide in the case of alkaline phosphatase. The amino acid composition of this peptide, which is comprised to 25 residues, was determined. Procaine (0.55% wt/vol) causes an increase in molecular packing of lipid molecules in the membrane which might result in an alteration of membrane fluidity sufficient for selective inhibition of processing of precursors of exported proteins.