Model of parkin directed ubiquitination of α-synuclein. The parkin protein consists of two functionally distinct regions. The UBL/UPD region binds target proteins such as glycosylated α-synuclein. The RING-box (RING1-IBR-RING2) region recruits specific E2 ubiquitin conjugating enzymes, which add ubiquitin monomers to the target protein. In addition to substrate binding the UBL domain interacts with the proteasome. Ubiquitin tagged α-synuclein is directed to the proteasome and degraded into polypeptides and ubiquitin monomers. UBL – Ubiquitin-like Domain, UPD – Unique Parkin Domain, RING1 or 2 – Really Interesting New Gene finger 1 or 2 domain, IBR – In-Between Ring domain.