AtPDIL5-1, an ER-resident putative thiol-disulfide oxidoreductase

Thiol-disulfide oxidoreductases are the principal actors of oxidative protein folding in the endoplasmic reticulum (ER)1. Due to the presence of at least one thioredoxin (TRX) domain containing the catalytic active CXXC motif, these proteins belong to the TRX superfamily. As ER resident proteins they also possess an N-terminal signal sequence and a C-terminal ER retention signal2. The most extensively studied member is PDI, Protein Disulfide Isomerase, which catalyzes the formation, reduction and isomerization of disulfide bonds and assists polypeptide folding1. The main differences among the PDI-like (PDIL) proteins essentially lie in the number and the position of TRX modules, in the active site sequence and in the presence of additional protein domains3. To date, only few studies have been performed to understand the physiological role of plant ER oxidoreductases, with the most documented function being their involvement in seed germination and development4. Here we present a preliminary characterization of the expression profile and the subcellular localization of AtPDIL5-1, a single TRX-domain PDIL protein from Arabidopsis thaliana.