Irreversible light-induced formation of P680+ and reduced cytochrome b559 in the D1-D2-Cyt b-559 complex at low temperature.
Cytochrome b559 in D1-D2-Cyt b-559 complexes from spinach can be photoreduced in the presence of DBMIB at a temperature of 180-240 K upon continuous illumination. The reduction of Cyt b-559 is accompanied by oxidation of P680. At 240 K recombination of P680+ and reduced Cyt b-559 is complete in several seconds. At 220 K and below, the state P680+Cyt b-559red can be trapped for a long time. This indicates that the photoreduced heme is incapable of electron transfer to P680+ at 220 K and below. On the other hand, the chemically reduced heme of Cyt b-559 is oxidized by P680+ at 77 K. These results are consistent with the presence of two kinds of Cyt b-559 hemes in D1-D2-Cyt b-559 complexes which participate in different ways in the photochemical reactions.
Kaminskaya
O P
OP
Institute of Soil Sciences and Photosynthesis, Russian Academy of Sciences, Pushchino, Moscow region.
Shuvalov
V A
VA
D003080:Cold Temperature; D003573:Cytochrome b Group / Q000378:metabolism*; D003624:Darkness; D003991:Dibromothymoquinone / Q000494:pharmacology; D004579:Electron Transport; D008027:Light; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D045332:Photosystem II Protein Complex; D013053:Spectrophotometry; D018724:Spinacia oleracea
D003573:Cytochrome b Group; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D003991:Dibromothymoquinone; C019313:cytochrome b559