Potential unrecognized redox-active atypical thioredoxins in eukaryote photosynthetic organisms.

Photosynthetic organisms have a high diversity of proteins belonging to the thioredoxin (TRX) superfamily. It comprises more than 150 proteins distributed in different families and classes, including in particular thioredoxins, glutaredoxins, protein disulfide isomerases, thiol peroxidases or glutathione transferases, which share the thioredoxin structural fold. Many of them have one or two redox-active cysteines and a characteristic cis-proline at specific positions, but also additional domains or secondary structures at either end or inserted into the protein core.

Redox regulation of enzymes involved in sulfate assimilation and in the synthesis of sulfur-containing amino acids and glutathione in plants.

Sulfur is essential in plants because of its presence in numerous molecules including the two amino acids, cysteine, and methionine. Cysteine serves also for the synthesis of glutathione and provides sulfur to many other molecules including protein cofactors or vitamins. Plants absorb sulfate from their environment and assimilate it a reductive pathway which involves, respectively, a series of transporters and enzymes belonging to multigenic families.