Glycoproteomics

Protein glycosylation involves the co-translational or post-translational addition of glycans to proteins and is a crucial protein modification in health and disease. The aim of glycoproteomics is to understand how glycosylation shapes biological processes by understanding peptide sequences, glycan structures and sites of modification in a system-wide context. Over the past two decades, mass spectrometry (MS) has emerged as the primary technique for studying glycoproteins, with intact glycopeptide analysis — the study of glycopeptides decorated with their native glycan structures — now a preferred approach across the community. In this Primer, we discuss glycoproteomic methods for studying glycosylation classes, including best practices and critical considerations. We summarize how glycoproteomics is used to understand glycosylation at a systems level, with a specific focus on N-linked and O-linked glycosylation (both mucin-type and O-GlcNAcylation). We cover topics that include sample selection; techniques for protein isolation, proteolytic digestion, glycopeptide enrichment and MS fragmentation; bioinformatic platforms and applications of glycoproteomics. Finally, we give a perspective on where the field is heading. Overall, this Primer outlines the current technologies, persistent challenges and recent advances in the exciting field of glycoproteomics. Glycoproteomic techniques give information on the structure and location of glycan protein modifications. In this Primer, Bagdonaite et al. summarize these techniques, discuss best practices for their use and explore their applications, including identifying biomarkers of disease.