Formation of the α1‐microglobulin chromophore in mammalian and insect cells: a novel post‐translational mechanism?

FEBS Letters

Enghild, Jan J²  Åkerström, Bo¹  Bratt, Tomas¹ 

[1] Section for Molecular Signalling, Department of Cell and Molecular Biology, Lund University, PO box 94, S-221 00 Lund, Sweden;Department of Pathology, Duke University, Durham, NC, USA

关键词: α1-Microglobulin;    Protein HC;    Chromophore;    Insect cell;    Post-translational modification;    α1-m;    α1-microglobulin;    SDS-PAGE;    sodium dodecyl sulfate-polyacrylamide gel electrophoresis;    PBS;    phosphate-buffered saline;    Endo-GalNAc;    endo-N-acetyl-galactosaminidase;    N-glycan;    asparagine-linked oligosaccharide;    O-glycan;    threonine-linked oligosaccharide;    CHO;    carbohydrate;    Hi 5;    Trichoplusia ni..;   

DOI  :  10.1016/0014-5793(95)00206-O

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

α₁-Microglobulin is an immunosuppressive plasma protein synthesized by the liver. The isolated protein is yellow-brown, but the hypothetical chromophore has not yet been identified. In this work, it is shown that a human liver cell line, HepG2, grown in a completely synthetic and serum-free medium, secretes α₁-microglobulin which is also yellow-brown, suggesting a de novo synthesis of the chromophore by the cells. α₁-Microglobulin isolated from the culture medium of insect cells transfected with the gene for rat α₁-microglobulin is also yellow-brown, suggesting that the gene carries information about the chromophore. Reduction and alkylation or removal of N- or O-linked carbohydrates by glycosidase treatment did not reduce the colour intensity of the protein. An internal dodecapeptide (amino acid positions 70–81 in human α₁-microglobulin) was also yellow-brown. The latter results indicate that the chromophore is linked to the polypeptide. In conclusion, the results suggest that the α₁-microglobulin gene carries information activating a post-translational protein modification mechanism which is present in mammalian and insect cells.

【 授权许可】

Unknown