CRYSTAL STRUCTURE OF ESCHERICHIA COLI THIOREDOXIN REDUCTASE REFINED AT 2 ANGSTROM RESOLUTION: IMPLICATIONS FOR A LARGE CONFORMATIONAL CHANGE DURING CATALYSIS
This family includes both class I and class II oxidoreductases and also NADH oxidases and peroxidases. This domain is actually a small NADH binding domain within a larger FAD binding domain.
Thioredoxin reductase contains FAD and NADPH binding domains that are structurally similar to the corresponding domains of the related enzyme glutathione reductase. The relative orientation of these domains is, however, very different in the two enzymes: when the FAD domains of thioredoxin and glutathione reductases are superimposed, the NADPH domain of one is rotated by 66 degrees with respect to the other. The observed binding mode of NADP+ in thioredoxin reductase is non-productive in that the nicotinamide ring is more than 17 A from the flavin ring system. Thioredoxin reductase belongs to the class-II pyridine nucleotide-disulfide oxidoreductase family.
Defined by 3 residues: CYS:A-135CYS:A-138ASP:A-139