Biomaterial Database

Evidence for the modulation of Pseudomonas aeruginosa exotoxin A-induced pore formation by membrane surface charge density. 1994

D M Rasper, and A R Merrill

Department of Chemistry and Biochemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Ontario, Canada.

The lipid requirement for the binding of wild-type Pseudomonas aeruginosa exotoxin A (ETA) to model endosomal membrane vesicles was evaluated using a fluorescence quenching technique. The binding of toxin to monodisperse model membrane vesicles (0.1 micron diameter) composed of various molar ratios of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS) prepared by an extrusion method [Hope, M. J., et al. (1986) Chem. Phys. Lipids 40 89-107] was pH-dependent, with maximal binding observed at pH 4.0. Analysis of the binding curves indicated that the interaction of ETA with the membrane bilayer is dominated by a set of high-affinity binding sites (Kd = 2-8 microM; 60:40 (mol:mol) POPC/POPS large unilamellar vesicles (LUV)). The binding of toxin to membrane vesicles was highly pH-dependent, but was ionic strength-independent. Toxin-induced pore formation in the lipid bilayer, as measured by the release of the fluorescent dye, calcein, from LUV was pH-dependent, with optimal dye release occurring at pH 4.0. The rate of dye release from membrane vesicles decreased rapidly with increasing pH and approached zero at pH 6.0 and higher. The pKa for this process ranged over 4.3-4.5. Calcein release from LUV was also sensitive to changes in the ionic strength of the assay buffer, with maximal release occurring at 50 mM NaCl. Higher ionic strength medium resulted in a dramatic reduction in the rate of dye release from vesicles, indicating that the toxin-induced pore is modulated by ionic interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D007202	Indicators and Reagents	Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)	Indicator,Reagent,Reagents,Indicators,Reagents and Indicators
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008051	Lipid Bilayers	Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes.	Bilayers, Lipid,Bilayer, Lipid,Lipid Bilayer
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D010713	Phosphatidylcholines	Derivatives of PHOSPHATIDIC ACIDS in which the phosphoric acid is bound in ester linkage to a CHOLINE moiety.	Choline Phosphoglycerides,Choline Glycerophospholipids,Phosphatidyl Choline,Phosphatidyl Cholines,Phosphatidylcholine,Choline, Phosphatidyl,Cholines, Phosphatidyl,Glycerophospholipids, Choline,Phosphoglycerides, Choline
D010718	Phosphatidylserines	Derivatives of PHOSPHATIDIC ACIDS in which the phosphoric acid is bound in ester linkage to a SERINE moiety.	Serine Phosphoglycerides,Phosphatidyl Serine,Phosphatidyl Serines,Phosphatidylserine,Phosphoglycerides, Serine,Serine, Phosphatidyl,Serines, Phosphatidyl
D011550	Pseudomonas aeruginosa	A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. aeruginosa is a major agent of nosocomial infection.	Bacillus aeruginosus,Bacillus pyocyaneus,Bacterium aeruginosum,Bacterium pyocyaneum,Micrococcus pyocyaneus,Pseudomonas polycolor,Pseudomonas pyocyanea
D002463	Cell Membrane Permeability	A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.	Permeability, Cell Membrane
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli