To enrich our knowledge about redox regulation mechanisms in chloroplasts, we selected two candidate chloroplastic proteins from Arabidopis thaliana, annotated as proteins of the thioredoxin superfamily and of unknown function. These thioredoxin-like proteins are present in all plants and share an AhpC-TSA_2 domain. The corresponding recombinant proteins have been produced and purified as mixture of holoforms ligating an iron-sulfur cluster and apoforms. The resolution of the structure of a monomeric apo-Trx-like 3 indicates that the CxxC motif is present in the first alpha-helix as expected, but that three N-terminal beta-strands and a C-terminal alpha-helix are present in addition to the AhpC domain. Despite the protein is efficiently oxidized by H2O2, no thiol peroxidase activity has been detected so far. A reductase activity was not detected either, using insulin as a substrate. Further experiments are currently done to understand the biochemical properties of these proteins and to identify their potential partners.