EXAMINATION OF CATALYTIC ACTIVITY OF THE BETA-SUBUNIT ISOLATED FROM CHLOROPLAST COUPLING FACTOR-1

A simple and rapid procedure has been developed to isolate the subunit from chloroplast coupling factor 1 involving anion exchange HPLC. The beta subunit was mainly in the monomeric form, along with some quantities of trimer and more complex aggregates of the protein. Decreasing pH down to neutral values or heating resulted in shifting the equilibrium in the medium to the formation of polymeric forms of the beta subunit. By successive purification and fractionation of CF1 and beta subunit preparations, it was shown that the monomeric form of the beta subunit catalysed ATP-ADP gamma-phosphate exchange. However, it did not display ATPase or adenylate kinase activities. Aggregation of the beta subunit was accompanied by irreversible inactivation of its ATP-ADP exchange activity.