Fixation and Inactivation of Staphylococcal Leukocidin by Phosphatidylcholine and Ganglioside G M1 in Rabbit Polymorphonuclear Leukocytes

Abstract

Staphylococcal leukocidin is resolved by chromatography on carboxymethyl cellulose columns into two components, which are designated F (fast) and S (slow). Fixation and inactivation of both components were studied as follows. (i) Leukocidin activity was confined to the first 10 min of intoxication, and the maximal effect resulted from treating 10 6 rabbit peripheral polymorphonuclear leukocytes per 20 μl with 0.5 ng of each component of leukocidin. The S component was more responsible for the interaction with the leukocytes than the F component. (ii) The F component was inactivated by phosphatidylcholine at concentrations which corresponded to molar proportions of 1:1 and bound to [ 14 C]phosphatidylcholine at equimolar proportions. (iii) The S component was inactivated by ganglioside G M1 at 1:1 molar proportions, but not by any of the related glycolipids. Ganglioside G M1 also was precipitated with the S component by a gel diffusion technique. Subunit B of cholera toxin competitively inhibited the binding of the S component to rabbit leukocyte membranes. This indicates that ganglioside G M1 may resemble or be part of the receptor site for the S component.