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Metab Eng. 2018 May;47:488-495. doi: 10.1016/j.ymben.2018.04.014. Epub 2018 Apr 25.

A flow cytometric approach to engineering Escherichia coli for improved eukaryotic protein glycosylation.

Author information

1
Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, 120 Olin Hall, Ithaca, NY 14853 USA.
2
Glycobia Incorporated, 33 Thornwood Drive, Ithaca, NY 14850 USA.
3
Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
4
Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, 120 Olin Hall, Ithaca, NY 14853 USA. Electronic address: md255@cornell.edu.

Abstract

A synthetic pathway for production of the eukaryotic trimannosyl chitobiose glycan (mannose3-N-acetylglucosamine2, Man3GlcNAc2) and its transfer to specific asparagine residues in target proteins was previously engineered in Escherichia coli, providing this simple microbe with the ability to perform a complex post-translational protein modification. Here, we leveraged a flow cytometric fluorescence-based assay to improve Man3GlcNAc2 glycan biosynthesis in E. coli cells. Specifically, pathway improvements were identified, including reducing pathway enzyme expression levels and overexpressing nucleotide sugar biosynthesis genes, which enhanced production of lipid-linked Man3GlcNAc2 by nearly 50-fold to 13.9 μg/L. In turn, cells producing higher levels of the Man3GlcNAc2 substrate yielded up to 10 times more glycosylated acceptor protein (to ~ 14 mg/L) than their non-optimized counterparts. These results demonstrate the use of flow cytometry screening as a powerful tool for interrogating the surfaces of glyco-engineered bacteria and identifying meaningful improvements in glycan biosynthesis. We anticipate this approach will enable further optimization of bacterial glycan biosynthesis pathways using new strain engineering tools from metabolic engineering and synthetic biology.

KEYWORDS:

Asparagine-linked protein glycosylation; Glycoengineering; Glycoprotein expression; Glycosyltransferase; Oligosaccharyltransferase; Post-translational modification; Synthetic biology

PMID:
29702274
DOI:
10.1016/j.ymben.2018.04.014
[Indexed for MEDLINE]

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