Abstract
The attachment of ubiquitin to proteins (ubiquitylation) is a post-translational modification that regulates a diverse range of biological processes, including signal transduction, transcriptional regulation and receptor down-regulation. Many ubiquitylated proteins are subsequently degraded by the 26S proteasome. A cascade of enzymes comprising an E1 ubiquitin activating enzyme, an E2 ubiquitin conjugating enzyme and an E3 ubiquitin ligase facilitate ubiquitylation. E3s, which mediate the transfer of ubiquitin from the E2 to the substrate, are largely responsible for specifying substrates. Abnormalities in the regulation of E3s are associated with many diseases, including neurodegenerative diseases and cancers.
RING (really interesting new gene) domains are one of three domains that possess E3 activity. There are over 500 RING-type E3s making them the largest group of E3s in humans. However, the mechanism by which RING-type E3s facilitate the transfer of ubiquitin from the E2 to the substrate is poorly understood. Arkadia is an ubiquitin E3 ligase with a C-terminal RING domain. This project aimed to characterise Arkadia’s RING domain to gain a better understanding of how RING-type E3s facilitate ubiquitin transfer. Of particular interest was mechanisms that regulate activity and distinguish monomeric RING domains from dimeric RING domains.