ISC system FeS cluster assembly, IscX (IPR007479)

Short name: ISC_FeS_clus_asmbl_IscsX

Overlapping homologous superfamilies

Family relationships



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] [PMID: 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 [PMID: 16211402, PMID: 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 [PMID: 15937904].

This entry represents IscX proteins (also known as hypothetical protein YfhJ) that are part of the ISC system. IscX is active as a monomer. The structure of YfhJ is an orthogonal alpha-bundle [PMID: 15937904]. YfhJ is a small acidic protein that binds IscS, and contains a modified winged helix motif that is usually found in DNA-binding proteins [PMID: 16698547]. YfhJ/IscX can bind Fe, and may function as an Fe donor in the assembly of FeS clusters

GO terms

Biological Process

GO:0016226 iron-sulfur cluster assembly

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.