Helena Ostolaza

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Alpha-Hemolysin is an extracellular protein toxin (107 kDa) produced by some pathogenic strains of Escherichia coli. Although stable in aqueous medium, it can bind to lipid bilayers and produce membrane disruption in model and cell membranes. Previous studies had shown that toxin binding to the bilayer did not always lead to membrane lysis. In this paper,(More)
alpha-Haemolysin is a protein toxin (107 kDa) secreted by some pathogenic strains of E. coli. It binds to mammalian cell membranes, disrupting cellular activities and lysing cells. This paper describes the mechanism of alpha-haemolysin-induced membrane leakage, from experiments in which extrusion large unilamellar vesicles, loaded with fluorescent solutes,(More)
alpha-haemolysin, an extracellular protein toxin of Escherichia coli, is known to disrupt eukaryotic cell membranes. In spite of genetic evidence of Ca(2+)-binding motifs in its sequence, conflicting results are found in the literature on the requirement of divalent cations for the membranolytic activity of the toxin. Moreover, Ca(2+)-binding sites have not(More)
alpha-Haemolysin interaction with model membranes has been investigated by a 2-fold procedure. First, protein binding has been measured, by a direct method as well as through changes in the intrinsic fluorescence of the protein when incubated with liposomes and divalent cations. Then, the above results have been correlated with the protein lytic activity.(More)
An improved, straightforward purification procedure for E.coli alpha-haemolysin has been developed. The protein exists in the form of large aggregates, held together mainly by hydrophobic forces. In the presence of urea or other chaotropic agents, the size of the aggregates decreases, while the specific activity is increased.
Pro-haemolysin (approximately 110 kDa), the inactive precursor of the membrane-lytic toxin alpha-haemolysin, has been purified from an overproducing strain of Escherichia coli. Pro-haemolysin forms aggregates in aqueous media, like the mature protein, suggesting an amphipathic structure. Direct measurements of protein binding to liposomal membranes,(More)
alpha-Hemolysin (HlyA) from Escherichia coli is a protein toxin (1024 amino acids) that targets eukaryotic cell membranes, causing loss of the permeability barrier. HlyA consists of two main regions, an N-terminal domain rich in amphipathic helices, and a C-terminal Ca(2+)-binding domain containing a Gly- and Asp-rich nonapeptide repeated in tandem 11-17(More)
alpha-Haemolysin is an extracellular protein toxin (approximately 107 kDa) secreted by Escherichia coli that acts at the level of the plasma membranes of target eukaryotic cells. The nature of the toxin interaction with the membrane is not known at present, although it has been established that receptor-mediated binding is not essential. In this work, we(More)
Familial hypercholesterolemia (FH) is a common autosomal codominant disease with a frequency of 1:500 individuals in its heterozygous form. The genetic basis of FH is most commonly mutations within the LDLR gene. Assessing the pathogenicity of LDLR variants is particularly important to give a patient a definitive diagnosis of FH. Current studies of LDLR(More)
Escherichia coli alpha-hemolysin (HlyA) is a 107-kDa protein toxin with a wide range of mammalian target cells. Previous work has shown that glycophorin is a specific receptor for HlyA in red blood cells (Cortajarena, A. L., Goñi, F. M., and Ostolaza, H. (2001) J. Biol. Chem. 276, 12513-12519). The present study was aimed at identifying the(More)