E3 ubiquitin ligase RBR family (IPR031127)

Short name: E3_UB_ligase_RBR

Overlapping homologous superfamilies


Family relationships


This family of E3 ligases has a distinctive organisation of RING fingers called 'RING-betweenRING-RING' (RBR), characterised by two RING fingers with a cysteine-rich region called the 'in-between-RING' domain that separates them [PMID: 15152079, PMID: 19526189]. The domains in the RBR E3 ligases have been further named as RING1-BRcat-Rcat according to their structure and function: the C-terminal Rcat (required-for-catalysis) domain is essential for catalytic activity, whereas the central BRcat (benign-catalytic) domain adopts the same fold as the Rcat, but lacks a catalytic cysteine residue and ubiquitination activity [PMID: 24576094]. These ligases have a unique mechanism of elongating ubiquitin chains that distinguishes them from other E3 ligases [PMID: 21532592, PMID: 24469331].

On the basis of sequence conservation within the RBR segment, RBR proteins are assigned to 15 subfamilies (A-I, P, S, T, U, X, Z). There are two RBR proteins in the yeast Saccharomyces cerevisiae, six in Drosophila melanogaster, 10 in Caenorhabditis elegans, about 40 in Arabidopsis thaliana, around 23 in the zebrafish (Danio rerio), and about 15 in humans [PMID: 17367545]. One of the most studied proteins in this family is parkin, whose dysfunction is linked to the pathogenesis of early-onset Parkinson's disease [PMID: 21694720]. This entry also includes HOIP (HOIL-1-interacting protein, also known as RNF31) and HOIL-1 (haem-oxidized IRP2 ubiquitin ligase 1, also known as RBCK1) [PMID: 22863777] among others.

GO terms

Biological Process

GO:0016567 protein ubiquitination

Molecular Function

GO:0004842 ubiquitin-protein transferase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.