Eukaryotic precursor proteins are processed by Escherichia coli outer membrane protein OmpP

A new specific endopeptidase that cleaves eukaryotic precursor proteins has been found in Escherichia coli K but not in E. coli B strains. After purification, protein sequencing and Western blotting, the endopeptidase was shown to be identical with E. coli outer membrane protein OmpP [Kaufmann, A., Stierhof, Y.-D. & Henning, U. (1994) J. Bacteriol. 176, 359-367]. Further characterization of enzymatic properties of the new peptidase was performed. Comparison of the cleavage specificities of the newly found endopeptidase and that of rat mitochondrial processing peptidase (MPP) showed that patterns of proteolytic cleavage on the investigated precursor proteins by both enzymes are similar. By using three mitochondrial precursor proteins, the specificity assigned to OmpP previously, a cleavage position between two basic amino-acid residues, was extended to a three amino-acid recognition sequence. Positions +1 to +3 of this extended recognition site consist of an amino-acid residue with a small aliphatic side chain such as alanine or serine, a large hydrophobic residue such as leucine or valine followed by an arginine residue. Additionally, structural motifs of the substrate seem to be required for OmpP cleavage.