Fig. 2

MS-based approaches to identifying the ubiquitination sites followed by enrichment of ubiquitinated proteins. A Purification of ubiquitylated proteins using tagged ubiquitin. B Purification of ubiquitylated proteins using Ub antibody. C Purification of ubiquitylated proteins using UBDs. The ubiquitinated proteins are first purified by the corresponding materials and digested by trypsin. Then, the whole tryptic peptides are analyzed by LC–MS/MS, resulting in the ubiquitination identification from the complicated peptide pool