InterPro : IPR010236

Name  ISC system FeS cluster assembly, HscA chaperone Short Name  ISC_FeS_clus_asmbl_HscA
Type  Family Description  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][]. 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 [, ]. 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 [].The SUF system is an alternative pathway to the ISC system that operatesunder 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 []. 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 [], 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 []. Nif proteins involved in the formation of FeS clusters can also be found in organisms that do not fix nitrogen [].This entry represents the HscA chaperone protein from the SUF system. HscA (or Hsc66) is a specialised bacterial Hsp70-class molecular chaperone that participates in the assembly of iron-sulphur cluster proteins. HscA resembles DnaK, but belongs to a separate clade. HscA interacts with IscU, which is believed to serve as a template for Fe-S cluster formation. The HscA-IscU interaction is facilitated by the J-type co-chaperone protein HscB (or Hsc20), which binds to both HscA and IscU, bringing them into contact with each other. HscA recognises a conserved LPPVK sequence motif at positions 99-103 of IscU [].

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

1 Contains

Id Name Short Name Type
IPR018181 Heat shock protein 70, conserved site Heat_shock_70_CS Conserved_site

0 Found In

1 Parent Features

Id Name Short Name Type
IPR013126 Heat shock protein 70 family Hsp_70_fam Family

9 Publications

First Author Title Year Journal Volume Pages
Hwang DM A modular domain of NifU, a nitrogen fixation cluster protein, is highly conserved in evolution. 1996 J Mol Evol 43 536-40
Seidler A Incorporation of iron-sulphur clusters in membrane-bound proteins. 2001 Biochem Soc Trans 29 418-21
Barras F How Escherichia coli and Saccharomyces cerevisiae build Fe/S proteins. 2005 Adv Microb Physiol 50 41-101
Fontecave M Mechanisms of iron-sulfur cluster assembly: the SUF machinery. 2005 J Biol Inorg Chem 10 713-21
Lill R Mechanisms of iron-sulfur protein maturation in mitochondria, cytosol and nucleus of eukaryotes. 2006 Biochim Biophys Acta 1763 652-67
Shimomura Y Crystal structure of Escherichia coli YfhJ protein, a member of the ISC machinery involved in assembly of iron-sulfur clusters. 2005 Proteins 60 566-9
Sendra M The SUF iron-sulfur cluster biosynthetic machinery: sulfur transfer from the SUFS-SUFE complex to SUFA. 2007 FEBS Lett 581 1362-8
Ollagnier-de-Choudens S SufA/IscA: reactivity studies of a class of scaffold proteins involved in [Fe-S] cluster assembly. 2004 J Biol Inorg Chem 9 828-38
Tapley TL Preferential substrate binding orientation by the molecular chaperone HscA. 2004 J Biol Chem 279 28435-42

To cite PlanMine, please refer to the following publication:

Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)