Interaction of Phospholipase A of the E. coli Outer Membrane with the Inhibitors of Eucaryotic Phospholipases A2 and Their Effect on the Ca2+-Induced Permeabilization of the Bacterial Membrane

Abstract

Phospholipase A of the bacterial outer membrane (OMPLA) is a β-barrel membrane protein which is activated under various stress conditions. The current study examines interaction of inhibitors of eucaryotic phospholipases A₂--palmitoyl trifluoromethyl ketone (PACOCF₃) and aristolochic acid (AA)--with OMPLA and considers a possible involvement of the enzyme in the Ca²⁺-dependent permeabilization of the outer membrane of Escherichia coli. Using the method of molecular docking, it has been predicted that PACOCF₃ 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 PACOCF₃, AA, and bromophenacyl bromide inhibit the Ca²⁺-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 Ca²⁺ and heat shock. The cell viability was not affected by the eucaryotic phospholipases A₂ 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.

Isolate Specific Cold Response of Yersinia enterocolitica in Transcriptional, Proteomic, and Membrane Physiological Changes

“…Outer membrane phospholipase A (encoded by pldA), which is activated under various stress conditions, presents in the outer membrane of Gram-negative bacteria. Its possible role is maintaining the cell envelope integrity and permeabilization, which is related to temperature (Dekker, 2000;Belosludtsev et al, 2014). The different expressions of pldA gene and protein among isolates suggested the possible involvement of outer membrane phospholipase A in fluidity maintenance under cold stress.…”

Self-oscillating Water Chemiluminescence Modes and Reactive Oxygen Species Generation Induced by Laser Irradiation; Effect of the Exclusion Zone Created by Nafion

“…It is thus necessary to carry out some additional experiments, where one could measure the dependence of the content of dissolved O2 on the EZ contribution to the system. For this purpose, we studied the time behavior of the dissolved oxygen concentration in the liquid samples, contacting or not contacting the Nafion interface, with an Oxygraph-2k device (Oroboros Instruments Corp., Innsbruck, Austria) [27,28], capable of measuring the content of dissolved oxygen in real time. We used glass cylindrical cells with radius R = 7 mm and a height h, which were filled with water in such a way that the free volume missed.…”

“…The time of the signal accumulation and the periodicity of recording the data was 1 s. The efficiency of counting photons was about 10 %, as determined by the calibration experiments with Cherenkov radiation from the isotope 32 P [34]. The luminescence spectral range was estimated by using blue or red optical filters with the 99 % transmission of the light flow at 380~520 and 590~800 nm, respectively [28].…”