Unraveling <i>O</i>‑Glycan Diversity\nof Mucins: Insights from SmE Mucinase and Ultraviolet Photodissociation\nMass Spectrometry

Deciphering the pattern and abundance of <i>O</i>-glycosylation\nof mucin domain proteins, glycoproteins heavily implicated in cancer\nand other diseases, remains an ongoing challenge. Both the macro-\nand microheterogeneity of glycosylation complicates the analysis,\nmotivating the development of new strategies for structural characterization\nof this diverse class of glycoproteins. Here we combine digestion\nof mucin domain proteins using a targeted protease, Enhancin from <i>Serratia marcescens</i> (SmE), with ultraviolet photodissociation\n(UVPD) mass spectrometry to advance glycan mapping and elucidation\nof <i>O</i>-glycosylation trends of densely glycosylated\nmucin proteins. UVPD facilitates identification of <i>O</i>-glycoforms of mucin domain proteins TIM-1, MUC-1 and MUC-16. Additionally,\nUVPD elucidates several glycoforms of MUC-16 and contributes to the\ndiscovery of <i>O</i>-glycosylation across tandem repeats\nof MUC-1.