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 (By similarity). Acts as a critical negative regulator of cardiac hypertrophy and a positive inotropic regulator (PubMed:16809552, PubMed:18258855, PubMed:18929570). Required for hemoglobin maturation. Does not possess any thyoredoxin activity since it lacks the conserved motif that is essential for catalytic activity (By similarity). Homodimer; the homodimer is independent of 2Fe-2S clusters. Heterotrimer; forms a heterotrimeric complex composed by two BOLA2 molecules and one GLRX3 molecule; linked by [2Fe-2S] clusters. Interacts (via N-terminus) with PRKCQ/PKC-theta (By similarity). Interacts (via C-terminus) with CSRP3 (PubMed:18258855). Interacts with CSRP2 (PubMed:18258855). Under the plasma membrane (PubMed:18258855). After PMA stimulation, GLRX3 and PRKCQ/PKC-theta translocate to a more extended submembrane area (PubMed:18258855). In the Z line, found associated with CSRP3 (PubMed:18258855). The thioredoxin domain lacks the two redox-active cysteines. This strongly suggests that it lacks thioredoxin activity. Homozygous null mutants die in utero some time between 12.5 and 14.5 dpc. 12.5 dpc embryos have a smaller body size and hemorrhage in the head. Heterozygous mutants are fertile and show no abnormalities in growth and development, cardiomyocytes exhibit significantly reduced contractility. Transgenic mice with cardiac-specific Glrx3 overexpression show that it is a potent inhibitor of cardiac hypertrophy induced by pressure overload (transverse aortic constriction). In addition, overexpression dramatically increases the ventricular function and cardiomyocyte contractility.