School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
Anal Chem. 2017 Mar 21;89(6):3656-3663. doi: 10.1021/acs.analchem.6b05064. Epub 2017 Mar 8.
Protein glycosylation is highly diverse and essential for mammalian cell survival. Heterogeneous glycans may be bound to different amino acid residues, forming multiple types of protein glycosylation. In this work, unexpected protein S-GlcNAcylation on cysteine residues was observed to extensively exist in human cells through global and site-specific analysis of protein GlcNAcylation by mass spectrometry. Three independent experiments produced similar results of many cysteine residues bound to N-acetylglucosamine (GlcNAc). Among well-localized S-GlcNAcylation sites, several motifs with an acidic amino acid around the sites were identified, which strongly suggests that a particular type of enzyme is responsible for this modification. Clustering results show that glycoproteins modified with S-GlcNAc are mainly involved in cell-cell adhesion and gene expression. For the first time, we found that proteins were extensively bound to GlcNAc through the side chains of cysteine residues in human cells, and the current discovery further advances our understanding of protein glycosylation.
蛋白质糖基化具有高度的多样性，对于哺乳动物细胞的存活至关重要。不同的聚糖可能结合到不同的氨基酸残基上，形成多种类型的蛋白质糖基化。在这项工作中，通过质谱法对蛋白质糖基化进行全局和特异性分析，我们观察到在人类细胞中，半胱氨酸残基上的蛋白质 S-GlcNAcylation 广泛存在，这是出乎意料的。三个独立的实验产生了许多半胱氨酸残基与 N-乙酰葡萄糖胺（GlcNAc）结合的类似结果。在定位良好的 S-GlcNAcylation 位点中，鉴定出了几个在该位点周围具有酸性氨基酸的基序，这强烈表明存在一种特定类型的酶负责这种修饰。聚类结果表明，用 S-GlcNAc 修饰的糖蛋白主要参与细胞-细胞黏附和基因表达。我们首次发现，在人类细胞中，蛋白质通过半胱氨酸残基的侧链广泛地与 GlcNAc 结合，这一发现进一步加深了我们对蛋白质糖基化的理解。
