Chaudhri M, Steverding D, Kittelberger D, Tjia S, Overath P
Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany.
Proc Natl Acad Sci U S A. 1994 Jul 5;91(14):6443-7. doi: 10.1073/pnas.91.14.6443.
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 expression 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.
表达位点相关基因ESAG 6先前被认为与原生动物寄生虫布氏锥虫中的转铁蛋白结合有关。布氏锥虫菌株AnTat1.3的ESAG 6和密切相关的ESAG 7现在已使用杆状病毒表达系统在昆虫细胞中表达。仅在昆虫细胞中表达ESAG 6会产生一种约52 kDa的糖基化蛋白，该蛋白通过其C末端的糖基磷脂酰肌醇锚定与细胞表面相关。约42 kDa的ESAG 7产物也被糖基化，但缺乏糖基磷脂酰肌醇修饰，并且位于细胞内。当单独表达任何一种ESAG时，均未观察到转铁蛋白结合活性。然而，它们的表达导致ESAG 6和7产物形成细胞表面复合物，该复合物特异性结合转铁蛋白。这表明ESAG 6和7产物对于结合转铁蛋白都是必需且足够的。
