Biosynthesis and secretion of human interleukin 2 glycoprotein variants from baculovirus-infected Sf21 cells. Characterization of polypeptides and posttranslational modifications

Eur J Biochem. 1993 Jul 1;215(1):189-97. doi: 10.1111/j.1432-1033.1993.tb18022.x.


Human interleukin 2 (IL-2) and human IL-2 mutant proteins, with artificially introduced N-glycosylation or O-glycosylation sites, have been expressed in a lepidopteran cell line (Sf21, Spodoptera frugiperda) using recombinant baculovirus vectors. Only approximately 25% of the total recombinant IL-2 protein synthesized by Sf21 cells was secreted into the culture medium. Significant N-terminal truncations were detected in the secreted polypeptides (up to 85% of the molecules). Alanine and proline were absent in the major truncated forms; the first 3-5 amino acids were also absent in a small proportion of the purified proteins. The introduction of potential artificial O-glycosylation peptide sequences (..GGKAPTPPPK..), to the C-terminus or between positions 80 and 81 of the IL-2 polypeptide chain, resulted in the secretion of unglycosylated and O-glycosylated variant forms. Fast atom bombardment mass spectrometry, compositional analysis and methylation analysis, of the tryptic glycopeptide APTPPPK, revealed the presence of either GalNAc or the disaccharide Gal(beta 1-3)GalNAc as the only carbohydrate constituents attached exclusively to Thr in this peptide, in a specific ratio for each individual IL-2 mutant protein. The Gal(beta 1-3)GalNAc protein forms could be partially altered in vitro to mammalian-type glycoforms by porcine liver beta-galactoside alpha-2,3-sialyltransferase in the presence of CMP-N-acetylneuraminic acid. An IL-2 mutant form, with an 11-amino-acid peptide of human interferon-beta at position 4, which includes its only N-glycosylation site, had exclusively truncated proximally fucosylated oligomannosidic glycans; Man3GlcNAc[Fuc(alpha 1-6)]GlcNAc or Man2GlcNAc[Fuc(alpha 1-6)]GlcNAc structures, in a ratio of 3:1, were detected in the secreted proteins. No evidence was obtained for the presence of secreted proteins with complex oligosaccharide chains, irrespective of the cell-culture conditions used or the harvesting time, for infected cells with recombinant baculovirus constructs.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Baculoviridae / metabolism
  • Carbohydrate Sequence
  • Cell Line
  • Glycosylation
  • Humans
  • Interleukin-2 / biosynthesis*
  • Interleukin-2 / chemistry
  • Interleukin-2 / metabolism
  • Molecular Sequence Data
  • Moths
  • Peptide Mapping
  • Protein Processing, Post-Translational*
  • Recombinant Proteins / biosynthesis*


  • Interleukin-2
  • Recombinant Proteins