Monothiol glutaredoxin involved in mitochondrial iron-sulfur (Fe/S) cluster transfer (PubMed:16110529). Receives iron-sulfur clusters from scaffold protein ISCU and mediates their transfer to apoproteins, to the 4Fe/FS cluster biosynthesis machinery, or export from mitochondrion (PubMed:16110529). Required for normal hemoglobin biosynthesis (PubMed:16110529). Homodimer. Detected in embryonic intermediate cell mass (site of hematopoiesis), liver and heart. Lethal between 7 and 10 dpf. Embryos show hypochromia, and circulating blood cells are pale due to a defect in hemoglobin biosynthesis.