The thioredoxin system is a significant redox regulator in all organisms. Thioredoxins in bacteria are the major dithiol reductants in the cytosol (or an advanced equivalent to dithiotreitol of cells) thanks to the low redox potentials (Holmgren, 1985). In the genome of the studied model Streptomyces coelicolor A3(2) several genes were revealed which code proteins forming the thioredoxin system. It seems that this gram-positive soil bacteria have a very complex redox system, with a variety of reducing possibilities. In this work cloning, purification and characterization of further thioredoxins (TrxA2 and TrxA3) are described. Both proteins were overexpressed in E. coli cytoplasma as soluble active hexahistidine fusion proteins and isolated as homogenous substances.
