Summary: Scaffold protein Nfu/NifU N terminal
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Scaffold protein Nfu/NifU N terminal Provide feedback
This domain is found at the N terminus of NifU and NifU related proteins, and in the human Nfu protein. Both of these proteins are thought to be involved in the the assembly of iron-sulphur clusters .
Tong WH, Jameson GN, Huynh BH, Rouault TA; , Proc Natl Acad Sci U S A. 2003;100:9762-9767.: Subcellular compartmentalization of human Nfu, an iron-sulfur cluster scaffold protein, and its ability to assemble a [4Fe-4S] cluster. PUBMED:12886008 EPMC:12886008
Dos Santos PC, Smith AD, Frazzon J, Cash VL, Johnson MK, Dean DR; , J Biol Chem. 2004;279:19705-19711.: Iron-sulfur cluster assembly: NifU-directed activation of the nitrogenase Fe protein. PUBMED:14993221 EPMC:14993221
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR014824
Iron-sulphur (FeS) clusters are important cofactors for numerous proteins involved in electron transfer, in redox and non-redox catalysis, in gene regulation, and as sensors of oxygen and iron. These functions depend on the various FeS cluster prosthetic groups, the most common being [2Fe-2S] and [4Fe-4S] [PUBMED:16221578]. FeS cluster assembly is a complex process involving the mobilisation of Fe and S atoms from storage sources, their assembly into [Fe-S] form, their transport to specific cellular locations, and their transfer to recipient apoproteins. So far, three FeS assembly machineries have been identified, which are capable of synthesising all types of [Fe-S] clusters: ISC (iron-sulphur cluster), SUF (sulphur assimilation), and NIF (nitrogen fixation) systems.
The ISC system is conserved in eubacteria and eukaryotes (mitochondria), and has broad specificity, targeting general FeS proteins [PUBMED:16211402, PUBMED:16843540]. It is encoded by the isc operon (iscRSUA-hscBA-fdx-iscX). IscS is a cysteine desulphurase, which obtains S from cysteine (converting it to alanine) and serves as a S donor for FeS cluster assembly. IscU and IscA act as scaffolds to accept S and Fe atoms, assembling clusters and transfering them to recipient apoproteins. HscA is a molecular chaperone and HscB is a co-chaperone. Fdx is a [2Fe-2S]-type ferredoxin. IscR is a transcription factor that regulates expression of the isc operon. IscX (also known as YfhJ) appears to interact with IscS and may function as an Fe donor during cluster assembly [PUBMED:15937904].
The SUF system is an alternative pathway to the ISC system that operates under iron starvation and oxidative stress. It is found in eubacteria, archaea and eukaryotes (plastids). The SUF system is encoded by the suf operon (sufABCDSE), and the six encoded proteins are arranged into two complexes (SufSE and SufBCD) and one protein (SufA). SufS is a pyridoxal-phosphate (PLP) protein displaying cysteine desulphurase activity. SufE acts as a scaffold protein that accepts S from SufS and donates it to SufA [PUBMED:17350000]. SufC is an ATPase with an unorthodox ATP-binding cassette (ABC)-like component. No specific functions have been assigned to SufB and SufD. SufA is homologous to IscA [PUBMED:15278785], acting as a scaffold protein in which Fe and S atoms are assembled into [FeS] cluster forms, which can then easily be transferred to apoproteins targets.
In the NIF system, NifS and NifU are required for the formation of metalloclusters of nitrogenase in Azotobacter vinelandii, and other organisms, as well as in the maturation of other FeS proteins. Nitrogenase catalyses the fixation of nitrogen. It contains a complex cluster, the FeMo cofactor, which contains molybdenum, Fe and S. NifS is a cysteine desulphurase. NifU binds one Fe atom at its N-terminal, assembling an FeS cluster that is transferred to nitrogenase apoproteins [PUBMED:11498000]. Nif proteins involved in the formation of FeS clusters can also be found in organisms that do not fix nitrogen [PUBMED:8875867].
This domain is found at the N terminus of NifU (from NIF system) and NifU related proteins, and in the human Nfu protein. Both of these proteins are thought to be involved in the assembly of iron-sulphur clusters, functioning as scaffolds [PUBMED:12886008, PUBMED:14993221].
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|Molecular function||iron ion binding (GO:0005506)|
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|Number in seed:||107|
|Number in full:||1440|
|Average length of the domain:||85.90 aa|
|Average identity of full alignment:||34 %|
|Average coverage of the sequence by the domain:||36.69 %|
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build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||6|
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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 Nfu_N domain has been found. There are 3 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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