Determination of the relatedness of the soluble surface proteins of Trypanosoma brucei and Paramecium aurelia.

The soluble surface proteins isolated by Cross (1975) from Trypanosoma brucei are compared to those which occur on Paramecium aurelia. Calculations based on the amino acid residue data and the molecular weights of these surface antigens indicate that there is a considerable degree of similarity between the T. brucei and the P. aurelia proteins, and that in neither case can simple mutation be responsible for the differences of molecules within each family of antigens. The analyses are consistent with the suggestion that the P. aurelia system can serve as a model for the phenomenon of phase transformation (relapse syndrome) which occurs in trypanosomiasis.