2lvo

Structural highlights

Function

[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.^{[1] [2]} [AMFR_HUMAN] E3 ubiquitin-protein ligase that mediates the polyubiquitination of a number of proteins such as CD3D, CYP3A4, CFTR and APOB for proteasomal degradation. Component of a VCP/p97-AMFR/gp78 complex that participates in the final step of endoplasmic reticulum-associated degradation (ERAD). The VCP/p97-AMFR/gp78 complex is involved in the sterol-accelerated ERAD degradation of HMGCR through binding to the HMGCR-INSIG complex at the ER membrane and initiating ubiquitination of HMGCR. The ubiquitinated HMGCR is then released from the ER by the complex into the cytosol for subsequent destruction. Also acts as a scaffold protein to assemble a complex that couples ubiquitination, retranslocation and deglycosylation. Mediates tumor invasion and metastasis as a receptor for the GPI/autocrine motility factor.^{[3] [4] [5] [6]}

See Also

• Ubiquitin
• Ubiquitin protein ligase

References

1. ↑ 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
2. ↑ 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
3. ↑ Shimizu K, Tani M, Watanabe H, Nagamachi Y, Niinaka Y, Shiroishi T, Ohwada S, Raz A, Yokota J. The autocrine motility factor receptor gene encodes a novel type of seven transmembrane protein. FEBS Lett. 1999 Aug 6;456(2):295-300. PMID:10456327
4. ↑ Fang S, Ferrone M, Yang C, Jensen JP, Tiwari S, Weissman AM. The tumor autocrine motility factor receptor, gp78, is a ubiquitin protein ligase implicated in degradation from the endoplasmic reticulum. Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14422-7. Epub 2001 Nov 27. PMID:11724934 doi:10.1073/pnas.251401598
5. ↑ Song BL, Sever N, DeBose-Boyd RA. Gp78, a membrane-anchored ubiquitin ligase, associates with Insig-1 and couples sterol-regulated ubiquitination to degradation of HMG CoA reductase. Mol Cell. 2005 Sep 16;19(6):829-40. PMID:16168377 doi:10.1016/j.molcel.2005.08.009
6. ↑ Pabarcus MK, Hoe N, Sadeghi S, Patterson C, Wiertz E, Correia MA. CYP3A4 ubiquitination by gp78 (the tumor autocrine motility factor receptor, AMFR) and CHIP E3 ligases. Arch Biochem Biophys. 2009 Mar 1;483(1):66-74. doi: 10.1016/j.abb.2008.12.001., Epub 2008 Dec 10. PMID:19103148 doi:10.1016/j.abb.2008.12.001
7. ↑ Liu S, Chen Y, Li J, Huang T, Tarasov S, King A, Weissman AM, Byrd RA, Das R. Promiscuous Interactions of gp78 E3 Ligase CUE Domain with Polyubiquitin Chains. Structure. 2012 Oct 31. pii: S0969-2126(12)00373-5. doi:, 10.1016/j.str.2012.09.020. PMID:23123110 doi:http://dx.doi.org/10.1016/j.str.2012.09.020