Ubiquitin ligase (E3 ubiquitin ligase) is a protein that recruits an E2 ubiquitin-conjugating enzyme that has been loaded with ubiquitin, recognizes a protein substrate, and helps or right catalyzes the transfer of ubiquitin from the E2 to the protein substrate. E3 ligases interact with both the concentrate on protein and the E2 enzyme, and so impart substrate specificity to the E2. Frequently, E3s polyubiquitinate their substrate with Lys48-linked chains of ubiquitin, targeting the substrate for destruction by the proteasome. E3 ligases are also critical gamers in mobile cycle manage, mediating the degradation of cyclins, as very well as cyclin dependent kinase inhibitor proteins. The human genome encodes more than 600 putative E3 ligases, enabling for huge variety in substrates. Ubiquitin-mediated degradation of regulatory proteins performs crucial roles in the management of numerous procedures, which include mobile-cycle progression, signal transduction, transcriptional regulation, receptor down-regulation, and endocytosis. The ubiquitin program has been implicated in the immune reaction, improvement, and programmed cell loss of life.