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 quanti ties of trimer and more complex aggregates of the protein. Decreasing pH down to neutral values or heating resulted in shifting the equilibr ium in the medium to the formation of polymeric forms of the beta subu nit. By successive purification and fractionation of CF1 and beta subu nit preparations, it was shown that the monomeric form of the beta sub unit catalysed ATP-ADP gamma-phosphate exchange. However, it did not d isplay ATPase or adenylate kinase activities. Aggregation of the beta subunit was accompanied by irreversible inactivation of its ATP-ADP ex change activity.