This family describes ORC ubiquitin ligase 1 (previously known as RING finger protein 219 or RNF219). ORC ubiquitin ligase 1 is an E3 ubiquitin ligase essential for DNA replication origin activation during S phase. It functions as a replication origin selector and catalyzes the multi-mono-ubiquitination of a subset of chromatin-bound ORC3 and ORC5 during S-phase [].
This is the insertion domain of ORC subunit 3 (ORC3) predominantly found in chodates, arthropodes and vertebrates, located between the N-terminal AAA+-like subunit and the C-terminal winged-helix (WH) DNA-binding domain []. ORC3 is a component of the origin recognition complex (ORC) that binds origins of replication, required to assemble the pre-replication complex necessary to initiate DNA replication. This insertion domain forms a bi-lobed α-helical protuberancethat engages a short α-helix formed at the ORC6 C-terminal, allowing its binding to ORC1-5 subunits [], which constitute the ORC core [, ].