Hybridization of Solubilized Membrane Components from Different Mycoplasma Species by Reaggregation

Abstract

THE plasma membrane of mycoplasmas, like other biological membranes, is built of protein and lipid and possesses several properties which make it an attractive model for membrane studies¹. The molecular organization of the protein and lipid in the mycoplasma membrane has been much studied in recent years. Sodium dodecyl sulphate (SDS) has been shown to solubilize the membrane to separate protein–detergent and lipid–detergent micelles^2,3. In spite of the complete separation of the protein from the lipid by SDS, these components could reaggregate spontaneously and form typical triple-layered membranes on removal of the detergent by dialysis against an Mg²⁺-containing buffer^3–5. The re-formed membranes morphologically resembled the original membranes, and contained some of their enzymatic activities which resisted inactivation by the detergent (S. R., Ne'eman and Ohad, to be published). The spontaneous reassociation of solubilized membrane protein and lipid appears to be a general property of biological membranes, for it could be demonstrated with membranes of diverse origin^6–9. Closer investigation of this property may disclose the mechanisms governing the assembly of proteins and lipids into membrane structures, and possibly help in the understanding of membrane assembly in vivo. In the course of this investigation the question arose whether the solubilized membrane components of one organism will reaggregate with those of another organism to form a hybrid reaggregate. Because the reaggregate prepared from solubilized Mycoplasma laidlawii membranes was found to have no common antigens with the reaggregate of Mycoplasma gallisepticum membranes, and to differ in its buoyant density, we decided to use these membranes to investigate the specificity problem.