Characterization of the mycoplasma membrane proteins II. Solubilization and enzymic activities of Acholeplasma laidlawii membrane proteins

Abstract

Treatment of Acholeplasma laidlawii membranes with EDTA in low-ionic strength media released about 11% of the total membrane protein in a water-soluble form. The released protein fraction had no NADH oxidase, ATPase and p-nitrophenylphosphatase activities. The strongly ionic detergents sodium dodecyl sulfate and cetyltrimethylammonium bromide were more effective in the solubilization of A. laidlawii membranes than the nonionic detergents Triton X-100, Lubrol W or Brij 58. Sodium deoxycholate occupied an intermediate position. The solubilization of the membranes by detergents affected their NADH oxidase, ATPase and p-nitrophenylphosphatase activities in two antagonistic ways: activation and inactivation. The balance of these processes depended on the type and concentration of the detergent used and on the enzymic activity tested. The activation effect was most pronounced with low concentrations of the nonionic detergents and with p-nitrophenylphosphatase activity. Inactivation of the enzymes was most pronounced with sodium dodecyl sulfate and cetyltrimethylammonium bromide. The results of the present study favor the use of nonionic detergents for the solubilization and further fractionation of mycoplasma membrane proteins.