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Clostridium perfringens exotoxins. VI. Reactivity of perfringolysin O with thiol and disulfide compounds.

The reactivity of perfringolysin O with thiol and disulfide compounds was studied. The activation potency of thiols was roughly proportional to the reaction rate constants of 5,5'-dithiobis-(2-nitrobenzoic acid) with thiols, which should be inversely proportional to their oxidation-reduction potentials. 1,2-Dimercaptoethane, which had the highest rate constant, most potently activated the toxin among the thiols tested and 4,4'-dipyridyl disulfide, which is known to be one of the most potent thiol-disulfide exchanging reagents, strongly inhibited toxin activity. Toxin activity was also inhibited by other thiol inhibitors.

Clostridium perfringens

Alteration of human erythrocyte plasma membranes by perfringolysin O as revealed by freeze-fracture electron microscopy. Studies on Clostridium perfringens exotoxins V.

When human erythrocyte membranes were treated with perfringolysin O (Clostridium perfringens theta-toxin) and examined by electron microscopy after freeze-fracture, two ultrastructural alterations were observed in fracture faces of membrane. (1) A random aggregation of intramembranous particles was seen in the fracture face of the protoplasmic half (PF face) of all membranes treated with the toxin, even if at a low concentration (40 hemolytic units/ml). On the other hand, the aggregation in the fracture face of the exoplasmic half (EF face) was observed only in membranes treated with a high concentration (3300 hemolytic units/ml) for 2 h. (2) Round protrusions and "cavities" with 30 nm in diameter were visible in EF and PF faces of membranes treated with a high concentration, respectively. These structures were always protruded toward cytoplasmic side, but did not appear to form holes through the membrane. Ring and arc shaped structures with a dark center of 26 nm and a distinct border of 5 nm in width were observed when the toxin alone was negatively stained at a very high concentration (170,000 hemolytic units/ml). These structures were also produced in the presence of cholesterol even if the toxin concentration was low.

Bacterial Toxins

Antigenic relationships among thiol-activated cytolysins.

Cereolysin, streptolysin O, and perfringolysin O formed precipitin lines that completely fused when reacted with horse antitetanolysin by Ouchterlony immunodiffusion and formed precipitin lines that showed either partial or complete fusion when diffused against horse antistreptolysin O or antiperfringolysin O.

Animals

Use of the D4H Probe to Track Sterols in Yeast.

Cholesterol is a fundamental component of cellular membranes, and its organization, distribution, and recycling are tightly regulated. Cholesterol can form, together with other lipids and proteins, membrane nanodomains, which play important roles in membrane trafficking, the spatiotemporal organization of signal transduction, or the modulation of plasma membrane transporters, among others. Not surprisingly then, the misregulation of cholesterol biosynthetic and transport pathways has been related to numerous diseases, including neurodegenerative and metabolic disorders. Here, we focus on the cholesterol-binding domain 4 (D4) of perfringolysin O (PFO, theta toxin) and its use as a probe to define the dynamics and subcellular localization of yeast sterols using time-lapse live-cell fluorescence microscopy. In combination with drugs that acutely interfere with sterol synthesis, such as terbinafine, the probe can also be used to monitor in real-time the extraction of sterols from specialized endoplasmic reticulum subdomains named ERSES (endoplasmic reticulum sterol exit sites) by the OSBP-related protein Osh2.

Saccharomyces cerevisiae