RNF227

Model summary

A human RING-type E3 ubiquitin ligase that uses a catalytic zinc-binding module to transfer ubiquitin from E2 conjugating enzymes onto target proteins and a C-terminal adaptor region to engage substrates and localization factors. By assembling transient complexes and catalyzing ubiquitin attachment, it modulates protein turnover and trafficking pathways, with activity concentrated at Golgi-associated assemblies where ubiquitination fine-tunes vesicle formation and cargo sorting.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The N-terminus to mid-region is dominated by zinc-binding RING signatures: IPR013083 (Zinc finger, RING/FYVE/PHD-type homologous superfamily, residues 5–134) provides the overarching fold class; within it, IPR001841 (Zinc finger, RING-type domain, residues 18–81) and IPR027370 (Zinc finger, RING-type, eukaryotic domain, residues 18–57) define a canonical RING catalytic core that coordinates Zn2+ to stabilize an E2~Ub-binding platform. The catalytic heart is reinforced by IPR017907 (Zinc finger, RING-type, conserved site, residues 43–52), marking the invariant metal-chelating motif that positions the thioester-charged ubiquitin for transfer. The C-terminal half carries IPR027952 (DUF4632 domain, residues 117–187), a module frequently paired with RING E3s that contributes to substrate/adaptor recognition and subcellular targeting. The overall envelope of IPR051435 (RING finger E3 ubiquitin-protein ligases family, residues 11–186) confirms that this polypeptide is a member of the RING E3 ubiquitin ligase family. The ordered layout—an N-terminal RING catalytic module followed by a C-terminal DUF4632 adaptor—creates a two-part machine: the RING domain catalyzes ubiquitin transfer, while DUF4632 tunes specificity and localization.

2. 02

   This architecture causes ubiquitin-protein transferase activity.

   The RING core binds a ubiquitin-charged E2 and allosterically activates thioester-to-isopeptide transfer, which corresponds to GO:0004842 ubiquitin-protein transferase activity. The presence of multiple interaction-prone modules and a DUF that often mediates adaptor binding collectively necessitate multivalent contacts with substrates and cofactors, aligning with GO:0005515 protein binding as an inherent property of this scaffolded E3.

3. 03

   Catalytically competent RING E3s drive protein ubiquitination, so the immediate biological role is GO:0016567 protein ubiquitination.

   In a cellular context, such E3s frequently remodel trafficking pathways by ubiquitinating coat components, adaptors, or SNARE-associated factors. The DUF4632 tail suggests a role in assembling complexes rather than performing catalysis alone, consistent with pathway control rather than bulk degradation.

4. 04

   Cellular placement follows from function and modules.

   RING E3s of this class often operate on endomembranes where cargo sorting and vesicle formation occur. The combination of a soluble RING core and a targeting DUF supports peripheral association with membrane-proximal assemblies. This points to a Golgi-centered role, consistent with GO:0005794 Golgi apparatus, where ubiquitination can regulate Golgi-to-endosome traffic and Golgi integrity.

5. 05

   Mechanistically, I hypothesize that the RING domain recruits a cognate E2 (such as UBE2D or UBE2N families) and transfers ubiquitin to Golgi-associated substrates—likely coat/adaptor proteins or trafficking regulators—thereby tuning vesicle budding and cargo flow.

   The DUF4632 region likely binds adaptor proteins or cargo receptors that localize the ligase to Golgi subdomains. Consequently, the protein forms transient complexes with ubiquitin pathway components and Golgi machinery to modulate ubiquitin signaling at the Golgi interface.