D1 ' centers are less efficient than normal photosystem II centers

One prominent difference between the photosystem II (PSII) reaction center protein D1 ' in Synechocystis 6803 and normal D1 is the replacement of Phe- 186 in D1 with leucine in D1 '. Mutants of Synechocystis 6803 producing onl y D1 ', or containing engineered D1 proteins with Phe-186 substitutions, we re analyzed by 77 K fluorescence emission spectra, chlorophyll a fluorescen ce induction yield and decay kinetics, and flash-induced oxygen evolution. Compared to D1-containing PSII centers, D1 ' centers exhibited a 50% reduct ion in variable chlorophyll a fluorescence yield, while the flash-induced O -2 evolution pattern was unaffected. In the F186 mutants, both the P680(+)/ Q(A)(-) recombination and O-2 oscillation pattern were noticeably perturbed . (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation o f European Biochemical Societies.