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Photosynthetic Electron Transport In Genetically Altered Photosystem Ii Reaction Centers Of Chloroplasts, Robin A. Roffey, John H. Golebeck, C. Russ Hille, Richard T. Sayre

Department of Biochemistry: Faculty Publications

Using a cotransformation system to identify chloroplast transformants in Chlamydomonas reinhardtii, we converted histidine-195 of the photosystem H reaction center D1 protein to a tyrosine residue. The mutants were characterized by a reduced quantum efficiency for photosynthetic oxygen evolution, which varied in a pH-dependent manner, a reduced capacity to oxidize artificial donors to photosystem II, and P680⁺) reduction kinetics (microsecond) that were essentially similar to wild type. In addition, a dark-stable radical was detected by ESR in mutant photosystem II particles but not in wild-type particles. This radical was similar in g value and lineshape to chlorophyll …