Monothiol glutaredoxin involved in mitochondrial iron-sulfur (Fe/S) cluster transfer (PubMed:19442627). 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 (By similarity). Required for normal regulation of hemoglobin synthesis by the iron-sulfur protein ACO1 (By similarity). Homodimer. Interacts with ISCU. Interacts with BOLA1. Detected in bone, liver, muscle and kidney. Ubiquitously expressed at 7.5 dpc. At 8.5 dpc, preferential expression in yolk sac blood islands. Progressive down-regulation in maturing primitive red cells between 10.5 and 12.5 dpc. High expression in fetal liver at 12.5 dpc. Belongs to the glutaredoxin family. Monothiol subfamily.