Iron sulfur cluster assembly protein 1, mitochondrial

UniProtKB accession:  Q03020

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UniProtKB description:  Scaffold protein for the de novo synthesis of iron-sulfur (Fe-S) clusters within mitochondria, which is required for maturation of both mitochondrial and cytoplasmic [2Fe-2S] and [4Fe-4S] proteins. First, a [2Fe-2S] cluster is transiently assembled on the scaffold proteins ISU1 and ISU2. In a second step, the cluster is released from ISU1/ISU2, transferred to glutaredoxin GRX5, followed by the formation of mitochondrial [2Fe-2S] proteins, the synthesis of [4Fe-4S] clusters and their target-specific insertion into the recipient apoproteins. Cluster assembly on ISU1/ISU2 depends on the function of the cysteine desulfurase complex NFS1-ISD11, which serves as the sulfur donor for cluster synthesis, the iron-binding protein frataxin (YFH1) as the putative iron donor, and the electron transfer chain comprised of ferredoxin reductase ARH1 and ferredoxin YAH1, which receive their electrons from NADH. Fe-S cluster release from ISU1/ISU2 is achieved by interaction with the Hsp70 chaperone SSQ1, assisted by the DnaJ-like co-chaperone JAC1 and the nucleotide exchange factor MGE1. ISU1 is the major isoform in yeast, while ISU2 is not detectable in cells grown to stationary phase (PubMed:10588895, PubMed:12970193, PubMed:14741370, PubMed:15123690, PubMed:16341089, PubMed:16431909, PubMed:23615440, PubMed:25358379). Also involved in production of a sulfur precursor required for thiolation of cytoplasmic tRNAs (PubMed:31040179).