ISOLATION AND PROPERTIES OF PS-II MEMBRANE-FRAGMENTS DEPLETED OF THE NON HEME IRON CENTER

The functional properties and the content of non heme iron and cytochr ome b559 mere investigated by measuring flash induced transient change s of the relative fluorescence quantum yield and applying Mossbauer sp ectroscopy, It was found that untreated PS II membrane fragments conta in a heterogeneous population of two types of non heme iron centers an d about 2 cytochrome 6559 per PS II. Twofold treatment of these sample s with a recently described 'iron depletion' procedure (MacMillan, F., Lendzian, F., Renger, G. and Lubitz, W. (1995) Biochemistry 34, 3144- 8156) leads to a complete loss (below the detection limit of Mossbauer spectroscopy) of the non heme iron center while more than 50% of the PS II complexes retain the functional integrity for light induced form ation of the 'stable' radical pair Y-Z(OX) P680Pheo Q(A)(radical anion ). This sample type deprived of virtually all non heme iron in PS II p rovides a most suitable material for magnetic resonance studies that r equire an elimination of the interaction between Fe2+ and nearby radic als.