| Structural highlights
Function
[UB2D2_HUMAN] Accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In vitro catalyzes 'Lys-48'-linked polyubiquitination. Mediates the selective degradation of short-lived and abnormal proteins. Functions in the E6/E6-AP-induced ubiquitination of p53/TP53. Mediates ubiquitination of PEX5 and autoubiquitination of STUB1 and TRAF6. Involved in the signal-induced conjugation and subsequent degradation of NFKBIA, FBXW2-mediated GCM1 ubiquitination and degradation, MDM2-dependent degradation of p53/TP53 and the activation of MAVS in the mitochondria by DDX58/RIG-I in response to viral infection. Essential for viral activation of IRF3.[1] [2] [3] [4] [5] [6] [7] [8] [UBC_HUMAN] 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 lysosomal degradation; 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.[9] [10]
Publication Abstract from PubMed
RING ubiquitin ligases (E3) recruit ubiquitin-conjugate enzymes (E2) charged with ubiquitin (Ub) to catalyze ubiquitination. Non-covalent Ub binding to the backside of certain E2s promotes processive polyUb formation, but the mechanism remains elusive. Here, we show that backside bound Ub (UbB) enhances both RING-independent and RING-dependent UbcH5B-catalyzed donor Ub (UbD) transfer, but with a more prominent effect in RING-dependent transfer. UbB enhances RING E3s' affinities for UbcH5B-Ub, and RING E3-UbcH5B-Ub complex improves UbB's affinity for UbcH5B. A comparison of the crystal structures of a RING E3, RNF38, bound to UbcH5B-Ub in the absence and presence of UbB, together with molecular dynamics simulation and biochemical analyses, suggests UbB restricts the flexibility of UbcH5B's alpha1 and alpha1beta1 loop. UbB supports E3 function by stabilizing the RING E3-UbcH5B-Ub complex, thereby improving the catalytic efficiency of Ub transfer. Thus, UbB serves as an allosteric activator of RING E3-mediated Ub transfer.
Activation of a Primed RING E3-E2-Ubiquitin Complex by Non-Covalent Ubiquitin.,Buetow L, Gabrielsen M, Anthony NG, Dou H, Patel A, Aitkenhead H, Sibbet GJ, Smith BO, Huang DT Mol Cell. 2015 Mar 18. pii: S1097-2765(15)00131-8. doi:, 10.1016/j.molcel.2015.02.017. PMID:25801170[11]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Gonen H, Bercovich B, Orian A, Carrano A, Takizawa C, Yamanaka K, Pagano M, Iwai K, Ciechanover A. Identification of the ubiquitin carrier proteins, E2s, involved in signal-induced conjugation and subsequent degradation of IkappaBalpha. J Biol Chem. 1999 May 21;274(21):14823-30. PMID:10329681
- ↑ Saville MK, Sparks A, Xirodimas DP, Wardrop J, Stevenson LF, Bourdon JC, Woods YL, Lane DP. Regulation of p53 by the ubiquitin-conjugating enzymes UbcH5B/C in vivo. J Biol Chem. 2004 Oct 1;279(40):42169-81. Epub 2004 Jul 26. PMID:15280377 doi:10.1074/jbc.M403362200
- ↑ Windheim M, Peggie M, Cohen P. Two different classes of E2 ubiquitin-conjugating enzymes are required for the mono-ubiquitination of proteins and elongation by polyubiquitin chains with a specific topology. Biochem J. 2008 Feb 1;409(3):723-9. PMID:18042044 doi:10.1042/BJ20071338
- ↑ Chiang MH, Chen LF, Chen H. Ubiquitin-conjugating enzyme UBE2D2 is responsible for FBXW2 (F-box and WD repeat domain containing 2)-mediated human GCM1 (glial cell missing homolog 1) ubiquitination and degradation. Biol Reprod. 2008 Nov;79(5):914-20. doi: 10.1095/biolreprod.108.071407. Epub 2008, Aug 13. PMID:18703417 doi:10.1095/biolreprod.108.071407
- ↑ Grou CP, Carvalho AF, Pinto MP, Wiese S, Piechura H, Meyer HE, Warscheid B, Sa-Miranda C, Azevedo JE. Members of the E2D (UbcH5) family mediate the ubiquitination of the conserved cysteine of Pex5p, the peroxisomal import receptor. J Biol Chem. 2008 May 23;283(21):14190-7. doi: 10.1074/jbc.M800402200. Epub 2008 , Mar 22. PMID:18359941 doi:10.1074/jbc.M800402200
- ↑ Zeng W, Xu M, Liu S, Sun L, Chen ZJ. Key role of Ubc5 and lysine-63 polyubiquitination in viral activation of IRF3. Mol Cell. 2009 Oct 23;36(2):315-25. doi: 10.1016/j.molcel.2009.09.037. PMID:19854139 doi:10.1016/j.molcel.2009.09.037
- ↑ Zeng W, Sun L, Jiang X, Chen X, Hou F, Adhikari A, Xu M, Chen ZJ. Reconstitution of the RIG-I pathway reveals a signaling role of unanchored polyubiquitin chains in innate immunity. Cell. 2010 Apr 16;141(2):315-30. doi: 10.1016/j.cell.2010.03.029. PMID:20403326 doi:10.1016/j.cell.2010.03.029
- ↑ David Y, Ziv T, Admon A, Navon A. The E2 ubiquitin conjugating enzymes direct polyubiquitination to preferred lysines. J Biol Chem. 2010 Jan 8. PMID:20061386 doi:M109.089003
- ↑ Huang F, Kirkpatrick D, Jiang X, Gygi S, Sorkin A. Differential regulation of EGF receptor internalization and degradation by multiubiquitination within the kinase domain. Mol Cell. 2006 Mar 17;21(6):737-48. PMID:16543144 doi:S1097-2765(06)00120-1
- ↑ Komander D. The emerging complexity of protein ubiquitination. Biochem Soc Trans. 2009 Oct;37(Pt 5):937-53. doi: 10.1042/BST0370937. PMID:19754430 doi:10.1042/BST0370937
- ↑ Buetow L, Gabrielsen M, Anthony NG, Dou H, Patel A, Aitkenhead H, Sibbet GJ, Smith BO, Huang DT. Activation of a Primed RING E3-E2-Ubiquitin Complex by Non-Covalent Ubiquitin. Mol Cell. 2015 Mar 18. pii: S1097-2765(15)00131-8. doi:, 10.1016/j.molcel.2015.02.017. PMID:25801170 doi:http://dx.doi.org/10.1016/j.molcel.2015.02.017
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