Ubiquitin-conjugating enzyme

Ubiquitin—protein ligase
Identifiers
EC number 6.3.2.19
CAS number 74812-49-0
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO
Ubiquitin-conjugating enzyme, E2
Identifiers
Symbol UBQ-conjugat_E2
Pfam PF00179
InterPro IPR000608
SMART SM00212
PROSITE PDOC00163

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.

Relationships

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.[1]

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.[2]

Isozymes

The following human genes encode ubiquitin-conjugating enzymes:

See also

References

  1. ↑ 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.
  2. ↑ 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.

External links


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