Membrane proteins with molecular masses of 88, 90 and 150 kDa are responsible for binding of human immunoglobulin G Fc fragment to the native cells of Mycoplasma salivarium

Mycoplasma salivarium cells bound the Fc fragment of human immunoglobulin G. The activity was remarkablu enhanced by Mn⁺, but not by Mg²⁺ and Ca²⁺; significantly inhibited by D-mannose; and reduced by pronase treatment of the cells. About 90% of the cells treated with pronase were not disrupted. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins of the cells treated with pronase indicated that proteins with molecular masses of 88, 90 and 150 kDa (88 kp, 90 kp and 150 kp) were specifically digested. The results presented suggest that 88 kp, 90 kp and 150 kp, located in the outer surface of the cell membrane, are responsible for the activity of the M. salivarium cells and interact with a carbohydrate-containing moiety (D-mannose) of the Fc fragment in a Mn²⁺-dependent manner.