Thioredoxin Reductase 3 (TrxR3)

Thioredoxin reductases (EC 1.6.4.5), such as TXNRD3, are selenocysteine (sec)-containing flavoenzymes that maintain thioredoxins, small proteins that catalyze redox reactions, in the reduced state using the reducing power of NADPH. The predicted 579-amino acid TXNRD3 protein, which is 70% and 53% identical to TXNRD1 and TXNRD2, respectively, contains 2 N-terminal active-site redox cysteines, NADPH- and FAD-binding residues, a dimer interface domain, and a C-terminal sec residue. The 3-primer UTR of TXNRD3 has a SECIS element. Northern blot analysis revealed preferential expression of a 2.8-kb Txnrd3 transcript in mouse testis. Immunoblot analysis showed expression of a 65-kD Txnrd3 protein in mouse testis and liver.