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E. coli alpha-hemolysin: a membrane-active protein toxin

F M Goñi1, H Ostolaza

  • 1Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain. gbzoseth@lg.ehu.es

Brazilian Journal of Medical and Biological Research = Revista Brasileira De Pesquisas Medicas E Biologicas
|October 20, 1998
PubMed
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Alpha-hemolysin (HlyA) requires calcium ions for irreversible membrane insertion and cell leakage. This toxin disrupts membranes by transiently altering bilayer tension, not by forming pores.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Membrane Biophysics

Background:

  • Alpha-hemolysin (HlyA) is a bacterial toxin synthesized as a polypeptide.
  • HlyA undergoes intracellular activation via fatty acylation and extracellular activation by divalent cations like Ca2+.
  • Even without activation, HlyA exhibits amphipathic properties and self-aggregation tendencies.

Purpose of the Study:

  • To elucidate the role of Ca2+ binding in alpha-hemolysin's membrane interaction and lytic activity.
  • To investigate the mechanism by which alpha-hemolysin compromises membrane integrity.
  • To determine if HlyA activity is dependent on specific cell surface receptors.

Main Methods:

  • Biophysical characterization of alpha-hemolysin's amphipathic properties.

Related Experiment Videos

  • Analysis of Ca2+ binding effects on HlyA conformation and membrane interaction.
  • Studies on HlyA activity using model lipid bilayers and cell membranes.

    • Main Results:

    • Ca2+-binding exposes hydrophobic regions on HlyA, promoting self-aggregation and irreversible membrane insertion.
    • HlyA binding to membranes, facilitated by Ca2+, leads to cell/vesicle leakage.
    • Leakage results from transient bilayer disruption due to protein insertion and altered membrane tension, not pore formation.

    Conclusions:

    • Extracellular Ca2+ binding is crucial for alpha-hemolysin's irreversible membrane binding and cytolytic activity.
    • Alpha-hemolysin induces membrane damage through physical disruption rather than pore formation.
    • HlyA can lyse cells and model membranes, suggesting receptor-independent mechanisms are significant.