Physical characterization of the pore forming cytolysine fromGardnerella vaginalis

Abstract

The cytolytic toxin (CTox) produced by Gardnerella vaginalis is able to form voltage‐dependent cationic channels when incorporated in lipid membranes (Moran et al, 1991) FEBS Lett. 283, 317–320). Osmotic protection experiments show that toxin incorporated in human erythrocytes forms pores between 18 Å and 28 Å in diameter. A hypothesis of pore formation as a primary event to produce cytolysis is proposed. The CTox activity increases when cells are depolarized by increasing the extracellular K+ concentration, probably reflecting the voltage dependent character of CTox formed channels. The cytolytic effect of the toxin was prevented by low temperatures and was a function of the extracellular Ca2+ concentration, suggesting a Ca2+ influx as part of the lytic mechanism. Binding of CTox to erythrocytes was dependent on external Ca2+ and was less temperature‐dependent. Dose‐response analysis suggests cooperativity of the toxin for the lytic activity, although no direct evidence of oligomerization has been found.

Biochemical characteristics of Eiseniapore, a pore‐forming protein in the coelomic fluid of earthworms

“…To evaluate the equivalent diameter of pores formed by Eiseniapore, experiments were performed using sheep erythrocytes as described previously [50,51]. Sheep erythrocytes (2%) were suspended in NaCl/P i containing, at a concentration of 30 m m , one of the following osmotic protectors (the effective molecular diameters are given in parentheses): sucrose (0.9 nm), raffinose (1.3 nm), dextran 4 (3 nm), inulin (3.5 nm), poly(ethylene glycol) 4000 (4 nm) and poly(ethylene glycol) 6000 (5 nm).…”