Summary: TFIIB zinc-binding
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TFIIB zinc-binding Provide feedback
The transcription factor TFIIB contains a zinc-binding motif near the N-terminus. This domain is involved in the interaction with RNA pol II and TFIIF and plays a crucial role in selecting the transcription initiation site. The domain adopts a zinc ribbon like structure .
Chen HT, Legault P, Glushka J, Omichinski JG, Scott RA; , Protein Sci 2000;9:1743-1752.: Structure of a (Cys3His) zinc ribbon, a ubiquitous motif in archaeal and eucaryal transcription. PUBMED:11045620 EPMC:11045620
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This tab holds annotation information from the InterPro database.
InterPro entry IPR013137
Zinc finger (Znf) domains are relatively small protein motifs which contain multiple finger-like protrusions that make tandem contacts with their target molecule. Some of these domains bind zinc, but many do not; instead binding other metals such as iron, or no metal at all. For example, some family members form salt bridges to stabilise the finger-like folds. They were first identified as a DNA-binding motif in transcription factor TFIIIA from Xenopus laevis (African clawed frog), however they are now recognised to bind DNA, RNA, protein and/or lipid substrates [PUBMED:10529348, PUBMED:15963892, PUBMED:15718139, PUBMED:17210253, PUBMED:12665246]. Their binding properties depend on the amino acid sequence of the finger domains and of the linker between fingers, as well as on the higher-order structures and the number of fingers. Znf domains are often found in clusters, where fingers can have different binding specificities. There are many superfamilies of Znf motifs, varying in both sequence and structure. They display considerable versatility in binding modes, even between members of the same class (e.g. some bind DNA, others protein), suggesting that Znf motifs are stable scaffolds that have evolved specialised functions. For example, Znf-containing proteins function in gene transcription, translation, mRNA trafficking, cytoskeleton organisation, epithelial development, cell adhesion, protein folding, chromatin remodelling and zinc sensing, to name but a few [PUBMED:11179890]. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target.
This entry represents a zinc finger motif found in transcription factor IIB (TFIIB). In eukaryotes the initiation of transcription of protein encoding genes by the polymerase II complexe (Pol II) is modulated by general and specific transcription factors. The general transcription factors operate through common promoters elements (such as the TATA box). At least seven different proteins associate to form the general transcription factors: TFIIA, -IIB, -IID, -IIE, -IIF, -IIG, and -IIH [PUBMED:1633439].
TFIIB and TFIID are responsible for promoter recognition and interaction with pol II; together with Pol II, they form a minimal initiation complex capable of transcription under certain conditions. The TATA box of a Pol II promoter is bound in the initiation complex by the TBP subunit of TFIID, which bends the DNA around the C-terminal domain of TFIIB whereas the N-terminal zinc finger of TFIIB interacts with Pol II [PUBMED:8516312, PUBMED:8504927].
The TFIIB zinc finger adopts a zinc ribbon fold characterised by two beta-hairpins forming two structurally similar zinc-binding sub-sites [PUBMED:8564536]. The zinc finger contacts the rbp1 subunit of Pol II through its dock domain, a conserved region of about 70 amino acids located close to the polymerase active site [PUBMED:15024075]. In the Pol II complex this surface is located near the RNA exit groove. Interestingly this sequence is best conserved in the three polymerases that utilise a TFIIB-like general transcription factor (Pol II, Pol III, and archaeal RNA polymerase) but not in Pol I [PUBMED:15024075].
More information about these proteins can be found at Protein of the Month: Zinc Fingers [PUBMED:].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||zinc ion binding (GO:0008270)|
|Biological process||regulation of transcription, DNA-dependent (GO:0006355)|
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A clan of zinc-binding ribbon domains.
The clan contains the following 50 members:A2L_zn_ribbon Auto_anti-p27 Baculo_LEF5_C DNA_RNApol_7kD DUF1610 DUF1936 DUF2116 DUF2180 DUF2387 DZR Elf1 GATA NinF NOB1_Zn_bind Ogr_Delta OrfB_Zn_ribbon PhnA_Zn_Ribbon Prim_Zn_Ribbon Ribosomal_L32p Ribosomal_L37ae Ribosomal_S27 Ribosomal_S27e RNA_POL_M_15KD RRN7 Spt4 TF_Zn_Ribbon TFIIS_C Tnp_zf-ribbon_2 Topo_Zn_Ribbon Toprim_Crpt Trm112p UPF0547 zf-C4_Topoisom zf-CHC2 zf-DHHC zf-dskA_traR zf-FPG_IleRS zf-GRF zf-NADH-PPase zf-RanBP zf-ribbon_3 zf-TFIIB zinc-ribbons_6 zinc_ribbon_2 zinc_ribbon_4 zinc_ribbon_5 Zn-ribbon_8 Zn_ribbon_recom Zn_Tnp_IS1 Zn_Tnp_IS1595
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Curation and family details
|Seed source:||Pfam-B_1298 (release 17.0)|
|Number in seed:||71|
|Number in full:||1235|
|Average length of the domain:||42.80 aa|
|Average identity of full alignment:||34 %|
|Average coverage of the sequence by the domain:||11.75 %|
|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:||7|
|Download:||download the raw HMM for this family|
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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 TF_Zn_Ribbon domain has been found. There are 7 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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