E3 ubiquitin ligase catalyzing the covalent attachment of ubiquitin moieties onto substrate proteins. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Expressed in primary roots and leaves. Detected in vascular bundle tissues. Expressed in dry seeds. Increased expression throughout imbibition and germination and when radicle and shoots are emerging. Up-regulated during cell differentiation.