[^1]
| UBE2B Protein |
|---|
| Protein Name | Ubiquitin-Conjugating Enzyme E2 B |
| Gene | [UBE2B](/genes/ube2b) |
| UniProt ID | [P49411](https://www.uniprot.org/uniprot/P49411) |
| PDB ID | 1f45, 2y5w, 3zth |
| Molecular Weight | ~17 kDa (152 aa) |
| Subcellular Localization | Nucleus, Cytoplasm |
| Protein Family | Ubc family (E2 conjugating enzymes) |
| Expression | Ubiquitous; high in testis, brain |
UBE2B encodes ubiquitin-conjugating enzyme E2 B, also known as UbcH2, a member of the E2 enzyme family that catalyzes the transfer of ubiquitin to substrate proteins. The ubiquitin-proteasome system (UPS) is essential for cellular protein quality control, regulating protein degradation, signaling, DNA repair, and numerous other cellular processes 1. UBE2B has specialized functions in histone ubiquitination, DNA repair, and spermatogenesis, with emerging links to neurodegenerative diseases 2.
UBE2B contains the characteristic UBC (Ubiquitin-Conjugating) domain:
- UBC core (~150 aa): Contains the active site and ubiquitin-binding surfaces
- Active site cysteine: Cys88 forms the thioester bond with ubiquitin
- HPPN loop: Contains the active site histidine
- Diversified N-terminal region: Confers substrate specificity
The structure positions the active site cysteine for ubiquitin transfer and includes residues that interact with E1 activating enzymes and E3 ligases 3.
UBE2B is one of ~30-40 E2 enzymes in humans:
- Highly conserved across eukaryotes
- Exists as a single isoform
- Structurally related to UBE2A (97% identity)
UBE2B functions in the ubiquitin cascade:
E1-E2-E3 Cascade:
- Receives ubiquitin from E1 (ubiquitin-activating) enzyme
- Forms thioester intermediate (E2~Ub)
- Transfers ubiquitin to substrate with E3 ligase
Chain Assembly:
- Builds ubiquitin chains (K48, K63 linkages)
- Different linkages have different cellular functions
- UBE2B can synthesize various chain types
UBE2B is a major histone ubiquitin conjugating enzyme:
H2A Ubiquitination:
- Catalyzes H2A K119 monoubiquitination
- Associated with transcriptional repression
- PRC1 recruitment and function
H2B Ubiquitination:
- H2B K120 ubiquitination (H2Bub1)
- Transcriptional activation
- DNA damage response
UBE2B participates in DNA damage responses:
Translesion Synthesis:
- Works with RAD18 E3 ligase
- PCNA ubiquitination (K164)
- Error-prone DNA repair
Chromatin Remodeling:
UBE2B is essential for male fertility:
- Required for chromatin condensation
- Protamine replacement in spermatids
- Essential for fertile sperm production
UBE2B alterations contribute to AD pathogenesis:
Protein Homeostasis:
- UPS dysfunction in AD brain
- UBE2B activity affected by Aβ
- Contributes to protein aggregate accumulation
Tau Pathology:
- Altered ubiquitination of tau
- Impaired clearance of pathological tau
- Contributes to NFT formation 4
Synaptic Function:
- Ubiquitination regulates synaptic proteins
- UBE2B affects AMPA receptor trafficking
- Contributes to synaptic dysfunction
α-Synuclein Clearance:
- UPS-mediated degradation of α-syn
- UBE2B may participate in clearance
- Dysfunction contributes to LB formation
LRRK2 Regulation:
- Interaction with LRRK2 pathway
- Possible role in PD pathogenesis
- May affect protein quality control 5
Mutant Huntingtin Clearance:
- UPS impairment in HD
- UBE2B involvement in clearance
- Contributes to aggregation
Transcription Dysregulation:
- H2A/H2B ubiquitination altered
- Affects gene expression
- May contribute to neuronal dysfunction
TDP-43 Pathology:
- UPS dysfunction in ALS
- TDP-43 aggregation
- UBE2B may regulate clearance
Protein Quality Control:
- Motor neurons vulnerable to proteostasis defects
- UBE2B activity important for clearance
- Contributes to degeneration 6
UPS Modulators:
- Enhancing E2 activity
- Activating protein clearance
- Reducing aggregation
E3 Ligase Modulators:
- Targeting specific ligases
- Affecting substrate selection
Proteasome Enhancers:
- Improving degradation capacity
- Reducing toxic protein accumulation
- UPS activity in blood/CSF
- Ubiquitination markers
- Disease progression indicators
- Located on chromosome 5q31.1
- Encodes 152 amino acid protein
- Essential gene (knockout lethal in mice)
- SNPs associated with disease risk
- Expression changes in neurodegeneration
- Possible therapeutic targeting
- Activity assays for E2 function
- Ubiquitin chain analysis
- Mass spectrometry proteomics
- Immunohistochemistry
- Knockout mice (Ube2b -/-)
- Drosophila models
- Cell culture systems
- Patient-derived neurons
- UBE2B structure and function. Nature, 1996.
- UBE2B in spermatogenesis. Nature, 2006.
- UBE2B catalytic mechanism. J Mol Biol, 2003.
- Ubiquitin system in AD. Nat Rev Neurol, 2013.
- UPS in PD pathogenesis. Nat Rev Neurol, 2014.
- Protein quality control in ALS. Nat Rev Neurol, 2014.