title: [Expression, purification and bioactivity evaluation of streptavidin-tagged human interleukin-21 fusion protein].
abstract: OBJECTIVE
  To obtain streptavidin-tagged human interleukin-21 (hIL21) fusion protein and evaluate its bioactivities.
  
  
  METHODS
  hIL21-SA-pET21 and pET24a-SA- hIL21 plasmids were constructed and expressed in BL21(DE3) host bacteria. The hIL21-SA and SA- hIL21 fusion protein were purified through Ni-NTA affinity chromatography and refolded by dialysis. Flow cytometry was used to detect hIL21-SA and SA- hIL21 fusion protein on the biotinylated MB49 tumor cells. MTT assay was used to evaluate the effect of the fusion protein on the proliferation of human peripheral blood lymphocytes (PBLs) stimulated by Anti-CD3.
  
  
  RESULTS
  The recombinant fusion proteins were highly expressed in BL21(DE3) at about 30% of the total bacterial proteins. The two fusion proteins exhibited bifunctional activities, i.e. both biotin-binding property and hIL21 activity and SA-mediated high-affinity binding to biotinylated cell surfaces (with anchoring modified rate of about 95.18% and 96.91%).
  
  
  CONCLUSIONS
  We have successfully obtained bifunctional fusion protein hIL21-SA and SA- hIL21,which will provide a basis for further study of tumor biotherapy using the proteins.
authors.affiliation: Institute of Biotherapy, School of Biotechnology, Southern Medical University, Guangzhou 510515, China. fapingping@sohu.com
authors.forename: Ping-ping
authors.initials: PP
authors.lastname: Fa
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jin-long
authors.initials: JL
authors.lastname: Li
authors.forename: Zhi-ming
authors.initials: ZM
authors.lastname: Hu
authors.forename: Ji-min
authors.initials: JM
authors.lastname: Gao
mesh_terms: D019496:Cancer Vaccines / Q000276:immunology; D045744:Cell Line, Tumor; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007378:Interleukins / Q000096:biosynthesis* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology*; D019809:Streptavidin / Q000096:biosynthesis* / Q000235:genetics; D000098546:Interleukin-21
chemical_list: D019496:Cancer Vaccines; D007378:Interleukins; D011993:Recombinant Fusion Proteins; D019809:Streptavidin; D000098546:Interleukin-21