Global site-specific analysis of glycoprotein N-glycan processing

Area of Science:

• Biochemistry
• Proteomics
• Glycobiology

Background:

• N-glycans are crucial for protein folding, stability, and function.
• The enzymatic processing of N-glycans results in complex glycoforms, complicating analysis.
• Site-specific glycosylation analysis is challenging due to the heterogeneity of glycan structures.

Purpose of the Study:

• To develop a robust semiquantitative mass spectrometry (MS)-based method for analyzing N-glycosylation.
• To determine the degree of glycan occupancy and processing at each glycosite.
• To provide a method applicable to virtually any glycoprotein with minimal sample input.

Main Methods:

• Proteolytic digestion of glycoproteins followed by protease denaturation.
• Sequential treatment with endoglycosidases Endo H and PNGase F to generate distinct mass signatures.
• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) for peptide identification and quantitation across three glycosylation states.

Main Results:

• The method accurately determines site-specific glycan occupancy and the proportion of N-glycans processed from high-mannose to complex types.
• Achieved full coverage of site-specific glycosylation with thousands of high-confidence spectral hits per glycosite.
• The complete analysis requires only 30 μg of protein and can be performed in approximately 7 days.

Conclusions:

• This developed MS-based method offers a powerful tool for detailed characterization of glycoprotein glycosylation.
• The protocol is robust, efficient, and accessible to researchers with basic proteomics skills.
• Enables comprehensive understanding of glycosylation patterns and their impact on protein function.