Summary: Ubiquitin-conjugating enzyme
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Ubiquitin-conjugating enzyme Edit Wikipedia article
|PDB structures||RCSB PDB PDBe PDBsum|
|Gene Ontology||AmiGO / EGO|
|Ubiquitin-conjugating enzyme, E2|
Ubiquitin-conjugating enzymes, also known as E2 enzymes and more rarely as ubiquitin-carrier enzymes, perform the second step in the ubiquitination reaction that targets a protein for degradation via the proteasome.The ubiquitination process covalently attaches ubiquitin, a short protein of 76 amino acids, to a lysine residue on the target protein. Once a protein has been tagged with one ubiquitin molecule, additional rounds of ubiquitination form a polyubiquitin chain that is recognized by the proteasome's 19S regulatory particle, triggering the ATP-dependent unfolding of the target protein that allows passage into the proteasome's 20S core particle, where proteases degrade the target into short peptide fragments for recycling by the cell.
A ubiquitin-activating enzyme or E1 first activates the ubiquitin by covalently attaching the molecule to its active site cysteine residue. The activated ubiquitin is then transferred to an E2 cysteine. Once conjugated to ubiquitin, the E2 molecule binds one of several ubiquitin ligases or E3s via a structurally conserved binding region. The E3 molecule is responsible for binding the target protein substrate and transferring the ubiquitin from the E2 cysteine to a lysine residue on the target protein.
A particular cell usually contains only a few types of E1 molecule, a greater diversity of E2s, and a very large variety of E3s. The E3 molecules responsible for substrate identification and binding are thus the mechanisms of substrate specificity in proteasomal degradation. Each type of E2 can associate with many E3s.
The following human genes encode ubiquitin-conjugating enzymes:
- UBE2D1, UBE2D2, UBE2D3, UBE2D4 (the latter putative)
- UBE2E1, UBE2E2, UBE2E3
- UBE2F (putative)
- UBE2G1, UBE2G2
- UBE2J1, UBE2J2
- UBE2L3, UBE2L6; (UBE2L1, UBE2L2, UBE2L4 are pseudogenes)
- UBE2Q1, UBE2Q2
- UBE2R1 (CDC34), UBE2R2
- UBE2T (putative)
- UBE2U (putative)
- UBE2V1, UBE2V2
- UBE2W (putative)
- Nandi, D; Tahiliani, P; Kumar, A; Chandu, D (2006). "The ubiquitin-proteasome system". Journal of biosciences 31 (1): 137–55. doi:10.1007/BF02705243. PMID 16595883.
- Risseeuw, EP; Daskalchuk, TE; Banks, TW; Liu, E; Cotelesage, J; Hellmann, H; Estelle, M; Somers, DE; Crosby, WL (2003). "Protein interaction analysis of SCF ubiquitin E3 ligase subunits from Arabidopsis". The Plant journal : for cell and molecular biology 34 (6): 753–67. doi:10.1046/j.1365-313X.2003.01768.x. PMID 12795696.
- Eukaryotic Linear Motif resource motif class MOD_SUMO
- Ubiquitin-Conjugating Enzymes at the US National Library of Medicine Medical Subject Headings (MeSH)
|This enzyme-related article is a stub. You can help Wikipedia by expanding it.|
Ubiquitin-conjugating enzyme Provide feedback
Proteins destined for proteasome-mediated degradation may be ubiquitinated. Ubiquitination follows conjugation of ubiquitin to a conserved cysteine residue of UBC homologues. TSG101 is one of several UBC homologues that lacks this active site cysteine [4, 5].
Cook WJ, Jeffrey LC, Xu Y, Chau V; , Biochemistry 1993;32:13809-13817.: Tertiary structures of class I ubiquitin-conjugating enzymes are highly conserved: crystal structure of yeast Ubc4. PUBMED:8268156 EPMC:8268156
Cook WJ, Martin PD, Edwards BF, Yamazaki RK, Chau V; , Biochemistry 1997;36:1621-1627.: Crystal structure of a class I ubiquitin conjugating enzyme (Ubc7) from Saccharomyces cerevisiae at 2.9 angstroms resolution. PUBMED:9048545 EPMC:9048545
Burroughs AM, Jaffee M, Iyer LM, Aravind L;, J Struct Biol. 2008;162:205-218.: Anatomy of the E2 ligase fold: implications for enzymology and evolution of ubiquitin/Ub-like protein conjugation. PUBMED:18276160 EPMC:18276160
Internal database links
|Similarity to PfamA using HHSearch:||UEV UFC1 Prok-E2_B|
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR000608
The post-translational attachment of ubiquitin (INTERPRO) to proteins (ubiquitinylation) alters the function, location or trafficking of a protein, or targets it to the 26S proteasome for degradation [PUBMED:15556404, PUBMED:15196553, PUBMED:15454246]. Ubiquitinylation is an ATP-dependent process that involves the action of at least three enzymes: a ubiquitin-activating enzyme (E1, INTERPRO), a ubiquitin-conjugating enzyme (E2), and a ubiquitin ligase (E3, INTERPRO, INTERPRO), which work sequentially in a cascade [PUBMED:14998368]. The E1 enzyme mediates an ATP-dependent transfer of a thioester-linked ubiquitin molecule to a cysteine residue on the E2 enzyme. The E2 enzyme (EC) then either transfers the ubiquitin moiety directly to a substrate, or to an E3 ligase, which can also ubiquitinylate a substrate.
There are several different E2 enzymes (over 30 in humans), which are broadly grouped into four classes, all of which have a core catalytic domain (containing the active site cysteine), and some of which have short N- and C-terminal amino acid extensions: class I enzymes consist of just the catalytic core domain (UBC), class II possess a UBC and a C-terminal extension, class III possess a UBC and an N-terminal extension, and class IV possess a UBC and both N- and C-terminal extensions. These extensions appear to be important for some subfamily function, including E2 localisation and protein-protein interactions [PUBMED:15545318]. In addition, there are proteins with an E2-like fold that are devoid of catalytic activity, but which appear to assist in poly-ubiquitin chain formation.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||acid-amino acid ligase activity (GO:0016881)|
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Curation and family details
|Author:||Ponting CP, Schultz J, Bork P, Finn RD|
|Number in seed:||71|
|Number in full:||9194|
|Average length of the domain:||134.10 aa|
|Average identity of full alignment:||27 %|
|Average coverage of the sequence by the domain:||49.81 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||21|
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There are 9 interactions for this family. More...
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the UQ_con domain has been found. There are 270 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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