UBB

This gene encodes ubiquitin, one of the most conserved proteins known. Ubiquitin has a major role in targeting cellular proteins for degradation by the 26S proteosome. It is also involved in the maintenance of chromatin structure, the regulation of gene expression, and the stress response. Ubiquitin is synthesized as a precursor protein consisting of either polyubiquitin chains or a single ubiquitin moiety fused to an unrelated protein. This gene consists of three direct repeats of the ubiquitin coding sequence with no spacer sequence. Consequently, the protein is expressed as a polyubiquitin precursor with a final amino acid after the last repeat. An aberrant form of this protein has been detected in patients with Alzheimer's disease and Down syndrome. Pseudogenes of this gene are located on chromosomes 1, 2, 13, and 17. Alternative splicing results in multiple transcript variants.

ubiquitin B

Ubiquitin
Exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in proteotoxic stress response and cell cycle; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling.

Biological Process energy homeostasis Source:Ensembl
Biological Process fat pad development Source:Ensembl
Biological Process female gonad development Source:Ensembl
Biological Process female meiosis I Source:Ensembl
Biological Process hypothalamus gonadotrophin-releasing hormone neuron development Source:Ensembl
Biological Process male meiosis I Source:Ensembl
Biological Process mitochondrion transport along microtubule Source:MGI1 Publication
Biological Process modification-dependent protein catabolic process Source:GO_Central1 Publication
Biological Process neuron projection morphogenesis Source:MGI1 Publication
Biological Process positive regulation of intrinsic apoptotic signaling pathway by p53 class mediator Source:MGI1 Publication
Biological Process positive regulation of protein monoubiquitination Source:ParkinsonsUK-UCL1 Publication
Biological Process positive regulation of protein ubiquitination Source:ParkinsonsUK-UCL1 Publication
Biological Process protein ubiquitination Source:GO_Central1 Publication
Biological Process regulation of mitochondrial membrane potential Source:MGI1 Publication
Biological Process regulation of neuron death Source:MGI1 Publication
Biological Process regulation of proteasomal protein catabolic process Source:MGI1 Publication
Biological Process seminiferous tubule development Source:Ensembl

Ubiquitin
Cytoplasm
Nucleus
Mitochondrion outer membrane

Ubiquitin
Phosphorylated at Ser-65 by PINK1 during mitophagy (PubMed:24660806, PubMed:24751536, PubMed:24784582, PubMed:25527291, PubMed:26161729).
Phosphorylated ubiquitin specifically binds and activates parkin (PRKN), triggering mitophagy (PubMed:24660806, PubMed:24751536, PubMed:24784582, PubMed:25527291, PubMed:26161729).
Phosphorylation does not affect E1-mediated E2 charging of ubiquitin but affects discharging of E2 enzymes to form polyubiquitin chains. It also affects deubiquitination by deubiquitinase enzymes such as USP30 (PubMed:25527291).
Ubiquitin
Mono-ADP-ribosylated at the C-terminus by PARP9, a component of the PPAR9-DTX3L complex. ADP-ribosylation requires processing by E1 and E2 enzymes and prevents ubiquitin conjugation to substrates such as histones.
Ubiquitin
(Microbial infection) Mono-ADP-ribosylated at Thr-66 by the C.violaceum CteC virulence factor. ADP-ribosylation causes the shutdown of polyubiquitin synthesis and disrupts the recognition and reversal of polyubiquitin.