Characterization of the Trypanosoma brucei homologue of a Trypanosoma cruzi flagellum-adhesion glycoprotein.

An immunodominant 72-kDa surface glycoprotein (Gp72) of Trypanosoma cruzi is involved in adhesion of the flagellum to the cell body (Cooper, R, Ribeiro de Jesus, A and Cross, G.A.M (1993) J. Cell Biol. 122, 149-156). We have characterized a gene, flagellum-adhesion glycoprotein genel (fla1), from Trypanosoma brucei that encodes a 546 amino-acid protein (Fla1) with high similarity to Gp72. Their sequence similarity and cellular localization suggest that Fla1 and Gp72 have similar functions. We could disrupt individual fla1 alleles but not both, suggesting that fla1 is essential in T. brucei, in contrast to the situation for gp72 in T. cruzi. Using affinity-purified polyclonal antibody, raised against part of the amino-terminal domain of Fla1 expressed in Escherichia coli, we showed that Fla1 is concentrated along the flagellum and in the flagellar pocket in both bloodstream-form and procyclic trypanosomes. Fla1 from both life-cycle stages is N-glycosylated. Fla1 from bloodstream-form T. brucei contains additional glycans, which can be liberated by treatment with mild acid, suggestive of phosphodiester linkages.