Abstract: A new protocol which is much simpler than current procedures, has been developed for purification of the Cyt b6f protein complex. The protocol contained only two steps dialysis-cen- trifugation and stepwise precipitation with ammonium sulfate. Moreover, this method is suitable for larger scale preparation. The purified complex from spinach ( Spinacia oleracea L. ) contained 9.8 nmol Cyt f per milligram protein. 2 Cyt b6(b-hemes) and 1 Chl a per Cyt f. SDS-PAGE showed four main bands and one weak band with low molecular weight. Its activity(PQ2H2→Cyt c)was around 80 μmol Cyt c·nmol Cyt f-1·h-l

Key words: Membrane protein, Cyt b6f complex, Purification