üks paljudest ensüümidest, mis seovad valgu külge ubikvitiini, mille tulemusena sageli suunatakse valk proteasoomidesse lagundamisele, A protein that recruits an E2 ubiquitin-conjugating enzyme that has been loaded with ubiquitin, recognizes a protein substrate, and assists or directly catalyzes the transfer of ubiquitin from the E2 to the protein substrate.