Chloroplast protease/chaperone AtDeg2 holds γ 1 subunit of ATP synthase in an unaggregated state under high irradiance conditions in Arabidopsis thaliana

Little data on the role played by chloroplast protein AtDeg2 as a chaperone is available. Therefore, we sought for chloroplast proteins protected from high irradiance-induced interprotein aggregation disulphide bridges by AtDeg2 acting as a holdase. To reach this goal, we performed analyses which involved comparative diagonal electrophoreses of lysates of chloroplasts isolated from wild type (WT) plants and transgenic plants which expressed AtDeg2 lacking its chaperone activity but retaining the protease activity. The results of the analyses indicate that AtDeg2 acting as a holdase prevents a single chloroplast protein, ., the γ subunit of ATP synthase from long-term high irradiance-induced homodimerization mediated by disuplhide bridges and this allows us to better understand a complexity of physiological significance of AtDeg2 - the chloroplast protein of dual protease/chaperone activity.