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Expression of a glycosylphosphatidylinositol-anchored Trypanosoma brucei transferrin-binding protein complex in insect cells

Chaudhri, M., Steverding, D., Kittelberger, D., Tjia, S., Overath, P.
Proceedings of the National Academy of Sciences of the United States of America 1994 v.91 no.14 pp. 6443-6447
Trypanosoma brucei, binding proteins, transferrin, structural genes, gene transfer, gene expression, cell lines, Spodoptera frugiperda, phosphatidylinositols, chemical reactions
The expression site-associated gene ESAG 6 was previously implicated in transferrin binding in the protozoan parasite Trypanosoma brucei. ESAG 6 and the closely related ESAG 7 of T. brucei strain AnTat1.3 have now been expressed in insect cells using the baculovirus expression system. Expression of ESAG 6 alone in insect cells gives rise to a glycosylated protein of approximately 52 kDa, which is cell surface-associated through a glycosylphosphatidylinositol anchor at its C terminus. The ESAG 7 product of about 42 kDa is also glycosylated, but lacks the glycosylphosphatidylinositol modification, and is located intracellularly. No transferrin-binding activity is observed when either ESAG is expressed independently. However, their coexpression results in a cell surface complex of ESAG 6 and 7 products that specifically binds transferrin. This shows that both ESAG 6 and 7 products are necessary and sufficient for binding to transferrin.