Evidence for lipid-protein interactions in the attachment of antigens to a low-density membrane fraction isolated from Trypanosoma rhodesiense.

A putative Trypanosoma rhodesiense flagella pocket membrane fraction (FPM) was previously found to possess a range of antigenic components that were released after exposure to a detergent mixture containing 0.1% Zwittergent 3-12 and 0.4% Triton X-100. In the present investigation, and effort was made to determine the role of membrane lipid in binding FPM antigens, using phospholipases A2 and C as membrane probes. Exposure to the former was notable for the release of one antigen in particular that was only poorly extracted with the above detergents. Evidence was obtained suggesting that this release was not due to the detergent action of degradation products formed by the action of phospholipase A2 on membrane phospholipids. This phospholipase-released antigen, as were most other FPM antigens, was a glycoprotein, although the carbohydrate sequences do not appear to influence antigenicity. It was also possible to demonstrate the presence of a group of three cross-reacting FPM antigens that partitioned as hydrophobic membrane proteins by using Triton X-114 extraction. This was in contrast to the predominantly hydrophilic nature of most other FPM antigens.