Influence of Cys-130 S. aureus Alpha-toxin on Planar Lipid Bilayer and Erythrocyte Membranes |
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Authors: | OV Krasilnikov M-FP Capistrano LN Yuldasheva RA Nogueira |
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Institution: | (1) Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, 700095 Tashkent, Uzbekistan, UZ;(2) Laboratory of Membrane Biophysics, Department of Biophysics and Radiobiology, Federal University of Pernambuco, 50670-901, Recife, PE, Brazil, BR;(3) Department of biochemistry, Tashkent Pediatric Medical Institute, 700125 Tashkent, Uzbekistan, UZ |
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Abstract: | Replacement of an amino acid residue at position 130 -Gly by Cys- in the primary structure of Staphylococcus aureus alpha-toxin
decreases the single-channel conductance induced by the toxin in planar lipid bilayers. Concomitantly, the pH value at which
the channel becomes unable to discriminate between Cl− and K+ ions is also decreased. By contrast, the pH dependence of the efficiency of the mutant toxin to form ion channels in lipid
bilayers was unchanged (maximum efficiency at pH 5.5–6.0). The asymmetry and nonlinearity of the current-voltage characteristics
of the channel were increased by the point mutation but the diameter of the water pore induced by the mutant toxin, evaluated
in lipid bilayers and in erythrocyte membranes, was found to be indistinguishable from that formed by wild-type toxin and
equal to 2.4–2.6 nm.
Alterations at the ``trans mouth' were found to be responsible for all observed changes of the channel properties. This mouth is situated close to
the surface of the second leaflet of a bilayer lipid membrane. The data obtained allows us to propose that the region around
residue 130 in fact determines the main features of the ST-channel and takes part in the formation of the trans entrance of the channel.
Received: 8 September 1995/Revised: 20 November 1996 |
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Keywords: | : Site-directed mutagenesis — Staphylotoxin — Planar lipid bilayer — Erythrocyte — Ion channel |
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