Absolute quantification analysis of ubiquitin chains attached to Nrf1 purified from NGLY1-KO cells overexpressing Nrf1-FLAG with HA-FBS2.

We examined ubiquitin-linkages on Nrf1 purified from cell lysates of NGLY1-KO cells overexpressing Nrf1-FLAG with HA-FBS2. The ubiquitin linkage types were quantified using the LC-MS/MS-based absolute quantification method, ubiquitin parallel reaction monitoring (Ub-AQUA/PRM).