Method for identifying ubiquitin-like modification sites of proteins

The main reasons are as follows: First, due to the dynamic and reversible nature of SUMOylation, the proportion of SUMOylated proteins in normal cells does not exceed 5% of the total protein, and many proteins can only be stimulated under specific conditions such as cell cycle, nutritional status, Heat shock, DNA damage, etc. will be modified by SUMOylation. How to enrich enough SUMOylated peptides for identification and eliminate the interference of unmodified peptides has always been a research difficulty; The molecular weight of the SUMO-modified peptide after enzyme digestion has a significant shift (SUMO-1 modification increases the molecular weight of the peptide by 2136Da, and SUMO-2 / 3 modification increases the molecular weight of the peptide by 3552Da). If the ratio is not within the detection range of mass spectrometry (400-1800), it cannot be selected for MS / MS sequence identification; third, when high molecular weight SUMOylated peptides are selected for collision-induced dissociation in primary mass spectrometry, due to Collision energy is limited, and often cannot provide sufficient fragment ions for sequence identification; fourth, unlike phosphorylation, the amino acid sequence of the SUMO modification will also undergo collision dissociation, making the entire SUMOylated peptide MS / MS The mass spectrum is quite complex

Despite attempts, there is currently no commercially available data analysis software that can perform high-throughput identification of these SUMO-modified MS / MS spectra to identify substrate peptide sequences and modification sites