Our research showed that PorB can be ubiquitinated in HeLa cells by an unidentified E3 ubiquitination ligase that catalyzes polyubiquitination of PorB. To identify the PorB-interacting E3 ubiquitin ligase, PorB and Ubiquitin were co-transfected to HeLa cells and PorB was immunoprecipitated. Subsequent analysis of co-immunoprecipitated proteins resulted in the identification of RNF213 as interacting E3 ubiquitin ligase.