Following Ariadne's thread: a new perspective on RBR ubiquitin ligases
1 Department of Biochemistry, University of Utah School of Medicine, 15 N. Medical Drive East, Salt Lake City, UT 84112-5650, USA
2 Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA
BMC Biology 2012, 10:24 doi:10.1186/1741-7007-10-24Published: 15 March 2012
Ubiquitin signaling pathways rely on E3 ligases for effecting the final transfer of ubiquitin from E2 ubiquitin conjugating enzymes to a protein target. Here we re-evaluate the hybrid RING/HECT mechanism used by the E3 family RING-between-RINGs (RBRs) to transfer ubiquitin to substrates. We place RBRs into the context of current knowledge of HECT and RING E3s. Although not as abundant as the other types of E3s (there are only slightly more than a dozen RBR E3s in the human genome), RBRs are conserved in all eukaryotes and play important roles in biology. Re-evaluation of RBR ligases as RING/HECT E3s provokes new questions and challenges the field.