REMOVAL OF NUCLEAR CONTAMINANTS AND OF NONSPECIFICALLY PHOTOSYSTEM II-BOUND COPPER FROM PHOTOSYSTEM-II PREPARATIONS

In conventional photosystem II preparation high amounts of Cu are foun d. After fractionation by centrifugation, Cu can be completely removed from photosystem II without affecting either its photosynthetic activ ity or the composition of its specific proteins. We could demonstrate that the Cu was associated with nuclear contaminants in the starch fra ction. Among the contaminants, several histones were identified by spe cific antisera and by N-terminal sequencing. In order to obtain homoge neous BBY preparations of PSII a procedure is employed that involves a 10 000 g centrifugation step and which eliminates non-specifically bo und metals, nucleic acids and histones with the starch pellet. The res ulting starch-free BBY (BBYs-), which is free of these nuclear contami nants, is an appropriate preparation for biophysical studies or for th ose of metal interactions with PSII.