Summary: U-box domain
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This tab holds annotation information from the InterPro database.
InterPro entry IPR003613
Quality control of intracellular proteins is essential for cellular homeostasis. Molecular chaperones recognise and contribute to the refolding of misfolded or unfolded proteins, whereas the ubiquitin-proteasome system mediates the degradation of such abnormal proteins. Ubiquitin-protein ligases (E3s) determine the substrate specificity for ubiquitylation and have been classified into HECT and RING-finger families. More recently, however, U-box proteins, which contain a domain (the U box) of about 70 amino acids that is conserved from yeast to humans, have been identified as a new type of E3 [PUBMED:12944364].
Members of the U-box family of proteins constitute a class of ubiquitin-protein ligases (E3s) distinct from the HECT-type and RING finger-containing E3 families [PUBMED:12944364]. Using yeast two-hybrid technology, all mammalian U-box proteins have been reported to interact with molecular chaperones or co-chaperones, including Hsp90, Hsp70, DnaJc7, EKN1, CRN, and VCP. This suggests that the function of U box-type E3s is to mediate the degradation of unfolded or misfolded proteins in conjunction with molecular chaperones as receptors that recognise such abnormal proteins [PUBMED:15115282, PUBMED:15189447].
Unlike the RING finger domain, INTERPRO, that is stabilised by Zn2+ ions coordinated by the cysteines and a histidine, the U-box scaffold is probably stabilised by a system of salt-bridges and hydrogen bonds. The charged and polar residues that participate in this network of bonds are more strongly conserved in the U-box proteins than in classic RING fingers, which supports their role in maintaining the stability of the U box. Thus, the U box appears to have evolved from a RING finger domain by appropriation of a new set of residues required to stabilise its structure, concomitant with the loss of the original, metal-chelating residues [PUBMED:10704423].
|Cellular component||ubiquitin ligase complex (GO:0000151)|
|Molecular function||ubiquitin-protein ligase activity (GO:0004842)|
|Biological process||protein ubiquitination (GO:0016567)|
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This clan includes the Ring zinc finger domains as well as the U-box domain that appears to have lost the zinc coordinating cysteine residues .
The clan contains the following 24 members:Baculo_RING FANCL_C Prok-RING_1 Prok-RING_2 Prok-RING_4 RINGv Rtf2 U-box zf-Apc11 zf-C3HC4 zf-C3HC4_2 zf-C3HC4_3 zf-C3HC4_4 zf-MIZ zf-Nse zf-rbx1 zf-RING-like zf-RING_2 zf-RING_4 zf-RING_5 zf-RING_6 zf-RING_UBOX zf-UBP zf-UDP
We make a range of alignments for each Pfam-A family:
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Curation and family details
|Seed source:||Pfam-B_2801 (release 7.5)|
|Number in seed:||16|
|Number in full:||2544|
|Average length of the domain:||70.60 aa|
|Average identity of full alignment:||32 %|
|Average coverage of the sequence by the domain:||11.07 %|
|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:||10|
|Download:||download the raw HMM for this family|
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There are 4 interactions for this family. More...
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 U-box domain has been found. There are 21 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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