Interaction of Phospholipase A of the E. coli Outer Membrane with the Inhibitors of Eucaryotic Phospholipases A^sub 2^ and Their Effect on the Ca^sup 2+^-Induced Permeabilization of the Bacterial Membrane

Phospholipase A of the bacterial outer membrane (OMPLA) is a [beta]-barrel membrane protein which is activated under various stress conditions. The current study examines interaction of inhibitors of eucaryotic phospholipases A^sub 2^--palmitoyl trifluoromethyl ketone (PACOCF^sub 3^) and aristolochic acid (AA)--with OMPLA and considers a possible involvement of the enzyme in the Ca^sup 2+^-dependent permeabilization of the outer membrane of Escherichia coli. Using the method of molecular docking, it has been predicted that PACOCF^sub 3^ and AA bind to OMPLA at the same site and with the same affinity as the OMPLA inhibitors, hexadecanesulfonylfluoride and bromophenacyl bromide, and the substrate of the enzyme palmitoyl oleoyl phosphatidylethanolamine. It has also been shown that PACOCF^sub 3^, AA, and bromophenacyl bromide inhibit the Ca^sup 2+^-induced temperature-dependent changes in the permeability of the bacterial membrane for the fluorescent probe propidium iodide and suppressed the transformation of E. coli cells with plasmid DNA induced by Ca^sup 2+^ and heat shock. The cell viability was not affected by the eucaryotic phospholipases A^sub 2^ inhibitors. The study discusses a possible involvement of OMPLA in the mechanisms of bacterial transmembrane transport based on the permeabilization of the bacterial outer membrane.[PUBLICATION ABSTRACT]