Little data on the role played in vivo by chloroplast protein AtDeg2 as a chaperone is available. Therefore, we sought for chloroplast proteins protected from high irradiance-induced interprotein aggregation via 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 35S:AtDEG2ΔPDZ1-GFP 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, i.e., the γ1 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.
Cation-induced aggrcgation of isolated LHC2 was ušed to compare the adliesion- promoting activities of individual LHCP2. Precipitated and waslied LHC2 of camation origin was aggregated in the presence of KCl. The polypeptide composition of the LHC2 sheets remaining in non-aggregated form after different tiine intervals was analysed by SDS-PAGE followed by scanning laser densitometiy. The LHC2 sheets enriched in a major camation LHC2-27 kDa polypeptide were shown to aggregate at a faster rate than the sheets enriched in minor LHCP2, i.e. 26 and 23 kDa polypeptides, although the finál degree of aggrcgation was similar for all types of LHC2 sheets.