Trypanosoma brucei: peptide mapping of partially homologous variable surface glycoproteins

Antigenic variation in Trypanosoma brucei is caused by amino acid sequence changes in a major surface glycoprotein. Each trypanosome may contain between 100 and 1000 genes coding for this glycoprotein. Some of these genes are members of partially homologous gene families. In addition, segments of different genes may combine to form 'hybrid' or 'mosaic' genes. Thus, surface glycoproteins exist containing varying amounts of amino acid sequence homology. For investigations of molecular mechanisms of antigenic diversity it is important to identify sub-sets of trypanosomes expressing related surface glycoproteins. We describe here a simple method based on trypanosome surface labeling followed by peptide mapping to indicate homologous peptides present in one sub-set of T. brucei surface glycoproteins.