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Electron donation by the high‐potential haems in Rhodopseudomonas viridis reaction centres at low temperatures
Author(s) -
Hubbard J.A.M.,
Evans M.C.W.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)81165-2
Subject(s) - redox , chemistry , photochemistry , cytochrome c , cytochrome , electron transfer , reduction potential , electron transport chain , heme , photosynthetic reaction centre , rhodopseudomonas palustris , stereochemistry , inorganic chemistry , biochemistry , biology , mitochondrion , enzyme , bacteria , genetics
EPR signals due to c ‐type cytochromes in Rhodopseudomonas viridis reaction centres are reported. Haems with E m = 380 mV (1), 310 mV (1) and about 0 mV (2) were identified. At redox potentials where the low‐potential cytochromes are oxidised, but the high‐potential cytochromes are reduced, photooxidation of the high‐potential cytochromes is observed as Q A is photoreduced by low‐temperature (15 K) illumination. Cyt c ‐556→cyt c ‐559→reaction centre→Q A However, the signal attributed to Q A is only 30–40% of the intensity and is narrower than that observed when Q A photoreduced with all the haems reduced. It is suggested that reduction of the low‐potential haems causes conformational changes in the reaction centre, altering the iron‐quinone interaction and the electron‐transfer process in the cytochrome chain.