Monothiol glutaredoxin involved in mitochondrial iron-sulfur (Fe/S) cluster transfer (PubMed:20364084, PubMed:23615440). Receives 2Fe/2S clusters from scaffold protein ISCU and mediates their transfer to apoproteins, to the 4Fe/FS cluster biosynthesis machinery, or export from mitochondrion (PubMed:20364084, PubMed:23615440, PubMed:24334290). Required for normal regulation of hemoglobin synthesis by the iron- sulfur protein ACO1 (PubMed:20364084). {ECO:0000269|PubMed:20364084, ECO:0000269|PubMed:23615440, ECO:0000269|PubMed:24334290}. This is the function of GLRX5 (glutaredoxin 5, ENSG00000182512).