Cytochrome c550 in the cyanobacterium Thermosynechococcus elongatus: study of redox mutants

The Journal of Biological Chemistry
Diana KirilovskyA William Rutherford

Abstract

Cytochrome c(550) is one of the extrinsic Photosystem II subunits in cyanobacteria and red algae. To study the possible role of the heme of the cytochrome c(550) we constructed two mutants of Thermosynechococcus elongatus in which the residue His-92, the sixth ligand of the heme, was replaced by a Met or a Cys in order to modify the redox properties of the heme. The H92M and H92C mutations changed the midpoint redox potential of the heme in the isolated cytochrome by +125 mV and -30 mV, respectively, compared with the wild type. The binding-induced increase of the redox potential observed in the wild type and the H92C mutant was absent in the H92M mutant. Both modified cytochromes were more easily detachable from the Photosystem II compared with the wild type. The Photosystem II activity in cells was not modified by the mutations suggesting that the redox potential of the cytochrome c(550) is not important for Photosystem II activity under normal growth conditions. A mutant lacking the cytochrome c(550) was also constructed. It showed a lowered affinity for Cl(-) and Ca(2+) as reported earlier for the cytochrome c(550)-less Synechocystis 6803 mutant, but it showed a shorter lived S(2)Q(B)(-) state, rather than a stabilized S(2)...Continue Reading

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Citations

Jan 4, 2007·Photosynthesis Research·Johnna L RooseHimadri B Pakrasi
Apr 22, 2008·Photosynthesis Research·Alain BoussacMiwa Sugiura
Nov 25, 2005·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Christopher C MoserP Leslie Dutton
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Mar 12, 2011·Journal of Photochemistry and Photobiology. B, Biology·Kunio IdoAnja Krieger-Liszkay
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Jan 31, 2018·PloS One·Akifumi NishidaMasayuki Yamamura
Mar 1, 2007·The Journal of Biological Chemistry·Christian FufezanDiana Kirilovsky
Feb 19, 2008·Biochemistry·Sebastián CarballalBeatriz Alvarez

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