| 15296447 |
Lim HJ, Kim YK, Hwang DS, Cha HJ: Expression of functional human transferrin in stably transfected Drosophila S2 cells. Biotechnol Prog. 2004 Jul-Aug;20(4):1192-7.
Human transferrin (hTf) is a serum glycoprotein involved in Fe3+ transport. Here, a plasmid encoding the hTf gene fused with a hexahistidine (His6) epitope tag under Drosophila metallothionein promoter (pMT) was stably transfected into Drosophila melanogaster S2 cells as a nonlytic plasmid-based system. Following 3 days of copper sulfate induction, transfected S2 cells were found to secrete hTf into serum-free culture medium at a competitively high expression level of 40.8 microg/mL, producing 6.8 microg/mL/day in a 150-mL spinner flask culture. Purification of secreted recombinant hTf using immobilized metal affinity chromatography (IMAC) yielded 95.5% pure recombinant hTf with a recovery of 32%. According to MALDI-TOF mass spectrometry analysis, purified S2 cell-derived His6-tagged recombinant hTf had a molecular weight (76.4 kDa) smaller than that of native apo-hTf (78.0 kDa). 2-Dimensional gel electrophoresis patterns showed recombinant hTf had a simpler and less acidic profile compared to that of native hTf. These data suggest recombinant hTf was incompletely (noncomplex) glycosylated and lacked sialic acids on N-glycans. However, this difference in N-glycan structure compared to native hTf had no effect on the iron-binding activity of recombinant hTf. The present data show that a plasmid-based stable transfection S2 cell system can be successfully employed as an alternative for producing secreted functional recombinant hTf. |
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