Interaction of alpha-latroinsectotoxin from Latrodectus mactans venom with bilayer lipid membranes
| Autor: | Evgeny V. Grishin, Oleg Ya. Shatursky, Oleg V. Bulgacov, Victor N. Pashkov |
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| Rok vydání: | 1995 |
| Předmět: |
Lipid Bilayers
Phospholipid Biophysics Latroinsectotoxin Spider Venoms Latrotoxin Biochemistry Ion Channels Divalent Membrane Potentials Potassium Chloride Lipid bilayer chemistry.chemical_compound Calcium Chloride Animals Black Widow Spider Ion channel Calcium ion channel selectivity chemistry.chemical_classification Ions Chromatography Bilayer Temperature Cooperative binding Conductance Cell Biology Crystallography Membrane chemistry Calcium |
| Zdroj: | Biochimica et biophysica acta. 1233(1) |
| ISSN: | 0006-3002 |
| Popis: | alpha-Latroinsectotoxin (LIT) from Latrodectus mactans venom increased the conductance of bilayer lipid membranes (BLM) by inducing channel like activity. The channels formed had a maximal single channel conductance of 5 pS in 10 mM CaCl2 solution. This process occurred more rapidly in symmetrical 10 mM CaCl2 solution than in equimolar KCl or NaCl. The LIT induced conductance showed pronounced rectification, that was dependent upon the face of the BLM to which the LIT was applied. This suggests that the LIT molecules incorporate into the bilayer lipid membrane in an oriented manner. The ion channels formed in bilayer phospholipid membrane by LIT are cation selective. The permeability of divalent cations decreased in the order Ba2+ > Ca2+ > Mg2+ > Cd2+ > Zn2+ (Zn2+ and Cd2+ blocked effectively LIT channels with the ratio of Ca2+trans and Cd2+cis or Zn2+cis of 1:1). Selectivity of LIT to monovalent cations was not high and was Ca2+ sensitive. Our data suggest that LIT has at least two Ca(2+)-binding sites, a high affinity site and low one (pK of binding is 2.4). As a result, the binding kinetics of Ca2+ with the toxin shows a high positive cooperativity (Hill coefficient, (h) = 5.95) and that dimerization might be a prerequisite to channel formation. Temperature dependence of conductance of LIT treated lipid bilayers in 100 mM KCl and 10 mM CaCl2 solutions was also determined: 18.9 +/- 2.11 kJ/mol and 28.537 +/- 1.678 kJ/mol, respectively. |
| Databáze: | OpenAIRE |
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