Fixation and Inactivation of Staphylococcal Leukocidin by Phosphatidylcholine and Ganglioside GM1 in Rabbit Polymorphonuclear Leukocytes

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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 106 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 [14C]phosphatidylcholine at equimolar proportions. (iii) The S component was inactivated by ganglioside GM1 at 1:1 molar proportions, but not by any of the related glycolipids. Ganglioside GM1 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 GM1 may resemble or be part of the receptor site for the S component.

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