Release of the variable surface coat glycoprotein from Trypanosoma brucei requires the cleavage of a phosphate ester

The membrane-bound and released forms of the variant surface coat glycoprotein from Trypanosoma brucei have been purified to homogeneity by a new rapid method in the absence of detergents. The conversion of the membrane-bound form to the released form has been found to consist of the cleavage of a phosphodiester bond, distal to the phosphate, linking the protein to a phospholipid. We suggest that this linkage constitutes the normal mode of attachment of the protein to the outer leaflet of the plasma membrane.