CHARACTERIZATION OF DETERGENT-SOLUBILIZED IODINE-125-LABELED ALPHA-TOXIN BOUND TO RABBIT ERYTHROCYTES AND MOUSE DIAPHRAGM MUSCLE

Triton X-100 extracts of staphylococcal l25l-labeled α-toxin-treated rabbit erythrocytes are resolved into two bands of radioactivity by sucrose density centrifugation and also by polyacrylamide disc gel analysis of sodium dodecyl sulfate extracts. The smaller band has an apparent molecular size of 2.8 × 104 daltons and comigrates with native α -toxin. The larger band has a molecular size of about 106 daltons and is remarkably stable to proteolytic digestion unless pretreated for 1 min at 100 °C in 2 M urea. Analysis by agarose-po-lyacrylamide slab gel electrophoresis of the sodium dodecyl sulfate extract permits resolution of the high molecular size band into two components of 1.5 × 106 and 1.1 × 106 apparent molecular weight. These forms are temperature sensitive and pretreatment for 1 min at 75 °C in sodium dodecyl sulfate causes disappearance of the 1.5 × 106 band and formation of a new band of 1.6 × 105 apparent molecular weight. Pre-treatment at 100 °C in sodium dodecyl sulfate causes all the radioactivity to migrate with native α-toxin. A model explaining these results in terms of formation of monomer and multimer complexes is reported. Antisera prepared against either a-toxin or rabbit erythrocyte membranes cause precipitation of the complex when assayed by the indirect precipitin method. That antisera to human erythrocytes, which do not specifically bind α-toxin, can also cause precipitation of 125I-labeled α-toxin-rabbit erythrocyte complexes remains unexplained. Extension of these observations with rabbit erythrocytes to other tissues in the mouse is reported. To date, only muscle tissue appears to bind α-toxin in a high molecular weight form analogous to that seen with rabbit erythrocytes. However, α-toxin bound to muscle appears to be “nonspecifically” bound. © 1979, American Chemical Society. All rights reserved.