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Updated: Aug 7, 2026
10:17
Pulse-chase Analysis of N-linked Sugar Chains from Glycoproteins in Mammalian Cells
Published on: April 27, 2010
Glycosylation site-binding protein is not required for N-linked glycoprotein synthesis
R Noiva1, H A Kaplan, W J Lennarz
1Department of Biochemistry and Molecular Biology, University of Texas-M.D. Anderson Cancer Center, Houston 77030.
Summary
Glycosylation site-binding protein (GSBP) was investigated for its role in protein N-glycosylation. Studies found no correlation between GSBP levels and oligosaccharyltransferase activity, suggesting it is not essential for this process.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- A 57-kDa protein, glycosylation site-binding protein (GSBP), was previously identified in the endoplasmic reticulum lumen.
- GSBP exhibits protein disulfide isomerase and thyroid hormone-binding activities, and binds to N-glycosylation site sequences.
- It was hypothesized that GSBP plays a role in protein N-glycosylation.
Purpose of the Study:
- To investigate the role of GSBP in the N-glycosylation process.
- To determine if GSBP is an essential component of oligosaccharyltransferase (OTase) activity.
Main Methods:
- Depletion of GSBP from the endoplasmic reticulum lumen under various conditions.
- Assessment of N-glycosylation levels catalyzed by OTase.
- Repletion of GSBP into the microsomal lumen to observe effects on OTase activity.
Main Results:
- Depletion of GSBP often resulted in partial loss of OTase activity, but this loss was independent of the extent of GSBP depletion.
- Complete depletion of GSBP (greater than 99%) was observed with partial retention of OTase activity.
- Repleting GSBP did not restore OTase activity to control levels, indicating no correlation between GSBP content and enzyme activity.
Conclusions:
- The multifunctional 57-kDa protein, GSBP, is not an essential component of the N-glycosylation enzymatic machinery.
- GSBP does not appear to be required for the transfer of oligosaccharide chains to nascent polypeptides or synthetic peptide acceptors.
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