Gianfranco Menestrina

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The interaction ofStaphylococcus aureus α-toxin with planar lipid membranes results in the formation of ionic channels whose conductance can be directly measured in voltage-clamp experiments. Single-channel conductance depends linearly on the solution conductivity suggesting that the pores are filled with aqueous solution; a rough diameter of 11.4±0.4 Å can(More)
The interaction ofActinia equina equinatoxin II (EqT-II) with human red blood cells (HRBC) and with model lipid membranes was studied. It was found that HRBC hemolysis by EqT-II is the result of a colloid-osmotic shock caused by the opening of toxin-induced ionic pores. In fact, hemolysis can be prevented by osmotic protectants of adequate size. The(More)
Actinaria cytolysins are very potent basic toxins isolated from the venom of sea anemones, which are supposed to exert their toxic activity through formation of oligomeric pores in the host plasma membrane. To gain insight into their mechanism of action, the interaction of Stichodactyla helianthus sticholysin I (St-I) with lipid bilayers was studied. St-I(More)
Intracellular activation of ricin and of the ricin A-chain (RTA) immunotoxins requires reduction of their intersubunit disulfide(s). This crucial event is likely to be catalyzed by disulfide oxidoreductases and precedes dislocation of the toxic subunit to the cytosol. We investigated the role of protein disulfide isomerase (EC, PDI), thioredoxin(More)
The radius of the pore formed by sticholysin I and II (StI, StII) in erythrocytes and sticholysin I in lipid vesicles was investigated. The rate of colloid osmotic lysis of human erythrocytes, exposed to one of the toxins in the presence of sugars of different size, was measured. The relative permeability of each sugar was derived and the pore radius(More)
Actinia equina equinatoxin II (EqT-II) is a representative of a family of pore-forming, basic, polypeptide toxins from sea anemones, now called actinoporins. This family comprises at least 27 members, which are all hemolytic at rather low concentrations. Red blood cell (RBC) hemolysis by EqT-II is the result of a colloid-osmotic shock caused by the opening(More)
Equinatoxin II is a cysteineless pore-forming protein from the sea anemone Actinia equina. It readily creates pores in membranes containing sphingomyelin. Its topology when bound in lipid membranes has been studied using cysteine-scanning mutagenesis. At approximately every tenth residue, a cysteine was introduced. Nineteen single cysteine mutants were(More)
Attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structure of two pore-forming cytolysins from the sea anemone Stichodactyla helianthus and their interaction with lipid membranes. Frequency component analysis of the amide I' band indicated that these peptides are composed predominantly of(More)
Equinatoxin II is a cytolytic polypeptide from the sea anemone Actinia equina L. which forms pores in natural and artificial membranes. The intrinsic fluorescence of its five tryptophanyl residues was used to monitor the conformational changes induced by denaturing agents, pH and lipids. In the presence of denaturants, the emitted fluorescence peak,(More)
Equinatoxin II is a representative of actinoporins, eukaryotic pore-forming toxins from sea anemones. It creates pores in natural and artificial lipid membranes by an association of three or four monomers. Cysteine-scanning mutagenesis was used to study the structure of the N terminus, which is proposed to be crucial in transmembrane pore formation. We(More)