Paradoxical lipid dependence of pores formed by the Escherichia coli alpha-hemolysin in planar phospholipid bilayer membranes.
alpha-Hemolysin (HlyA) is an extracellular protein toxin (117 kDa) secreted by Escherichia coli that targets the plasma membranes of eukaryotic cells. We studied the interaction of this toxin with membranes using planar phospholipid bilayers. For all lipid mixtures tested, addition of nanomolar concentrations of toxin resulted in an increase of membrane conductance and a decrease in membrane stability. HlyA decreased membrane lifetime up to three orders of magnitude in a voltage-dependent manner. Using a theory for lipidic pore formation, we analyzed these data to quantify how HlyA diminished the line tension of the membrane (i.e., the energy required to form the edge of a new pore). However, in contrast to the expectation that adding the positive curvature agent lysophosphatidylcholine would synergistically lower line tension, its addition significantly stabilized HlyA-treated membranes. HlyA also appeared to thicken bilayers to which it was added. We discuss these results in terms of models for proteolipidic pores.
Bakás
Laura
L
Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Chanturiya
Alexandr
A
Herlax
Vanesa
V
Zimmerberg
Joshua
J
D003198:Computer Simulation; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D008051:Lipid Bilayers / Q000737:chemistry*; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D010743:Phospholipids / Q000737:chemistry*; D016062:Porosity
D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D008051:Lipid Bilayers; D010743:Phospholipids