Glycosylation is the process by which a carbohydrate is covalently attached to target macromolecules, typically proteins. This modification serves various functions including guiding protein folding (1,2), promoting protein stability (2), and participating signaling functions (3).
SARS-CoV-2 utilizes an extensively glycosylated spike (S) protein that protrudes from the viral surface to bind to angiotensin-converting enzyme 2 (ACE2) to mediate host-cell entry. Vaccine development has been focused on this protein, which is the focus of the humoral immune response. Understanding the glycan structure of the SARS-CoV-2 virus spike (S) protein will be critical in the development of glycoprotine-based vaccine candidates.
In a recent publication from Wantanabe and colleagues, the site-specific glycosylation of SARS-CoV-2 and the glycan compositions were determined for all 22 N-linked glycan sites located on the S protein (4) using mass spectrometry.
The basic experimental design included the following steps:
- Expression of the SARS-CoV-2 S protein in human embryonic kidney 293F cells
- Purification of recombinant protein,
- Sample prep and digestion with trypsin or chymotrypsin (Promega), and
- Analysis by Liquid chromatography-mass spectrometry (LC/MS).
This glycosylation analysis of SARS-CoV-2 offers insight into the site-specific glycan content of the S protein. Glycoprotein-based vaccines for SARS-CoV-2 are a growing area of focus, and this information can aid in understanding immunogen integrity of vaccine candidates as they are developed.
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- Xu, C. and Ng, D.T.W. (2015) Glycosylation-directed quality control of protein folding. Nat. Rev. Mol. Cell Biol. 16, 742–52.
- Jayaparakash, N. and Surolia, A. (2017) Role of glycosylation in nucleating protein folding and stability. Biochem J. 474, 2333–47.
- Dewald, J.H. et al. (2016) Role of cytokine-induced glycosylation changes in regulating cell interactions and cell signaling in inflammatory diseases and cancer. Cells, 5. 10.3390/cells5040043
- Watanabe, Y. et al. (2020) Site Specific glycan analysis of the SARS-CoV-2 spike Science May 20.