Together with BOLA2, acts as a cytosolic iron-sulfur (Fe-S) cluster assembly factor that facilitates [2Fe-2S] cluster insertion into a subset of cytosolic proteins (PubMed:26613676, PubMed:27519415). Acts as a critical negative regulator of cardiac hypertrophy and a positive inotropic regulator (By similarity). Required for hemoglobin maturation (PubMed:23615448). Does not possess any thyoredoxin activity since it lacks the conserved motif that is essential for catalytic activity. Homodimer; the homodimer is independent of 2Fe-2S clusters (PubMed:27519415). Heterotrimer; forms a heterotrimeric complex composed by two BOLA2 molecules and one GLRX3 molecule; linked by [2Fe-2S] clusters (PubMed:22309771, PubMed:26613676, PubMed:27519415). Interacts (via N-terminus) with PRKCQ/PKC-theta (PubMed:10636891). Interacts (via C-terminus) with CSRP3 (By similarity). Interacts with CSRP2 (By similarity). Under the plasma membrane (By similarity). After PMA stimulation, GLRX3 and PRKCQ/PKC-theta translocate to a more extended submembrane area (By similarity). In the Z line, found associated with CSRP3 (By similarity). Expressed in heart, spleen, testis and, to a lower extent, in thymus and peripheral blood leukocytes. Weakly expressed in lung, placenta, colon and small intestine. The thioredoxin domain lacks the two redox-active cysteines. This strongly suggests that it lacks thioredoxin activity. Silencing of Grx3 in HeLa cells decreases the activities of several cytosolic Fe/S proteins, such as ACO1, a major component of post-transcriptional iron regulation. As a consequence, Grx3-depleted cells show decreased levels of ferritin and increased levels of transferrin receptor, features characteristic of cellular iron starvation (PubMed:23615448).