Mössbauer Studies of Cu(II) Ions Interaction with the Non-Heme Iron and Cytochrome b559 in a Chlamydomonas reinhardtii PSI Minus Mutant

K. Burda a, b, J. Krukc, K. Strzałkac, J. Staneka, G.H. Schmid d and O. Kruse d aInstitute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland bInstitute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków, Poland cFaculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland dUniversity of Bielefeld, Department of Biology, Molecular Cell Physiology, Universitaetsstr. 25, 33501 Bielefeld, Germany

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Received: 2005 20 05;

Mössbauer spectroscopy was applied, for the first time, to study the interaction of copper ions with the non-heme iron and the heme iron of cytochrome b559 in photosystem II thylakoids isolated from a Chlamydomonas reinhardtii photosystem I minus mutant. We showed that copper ions oxidize the heme iron and change its low spin state into a high spin state. This is probably due to deprotonation of the histidine coordinating the heme. We also found that copper preserves the non-heme iron in a low spin ferrous state, enhancing the covalence of iron bonds as compared to the untreated sample. We suggest that a disruption of hydrogen bonds stabilizing the quinone-iron complex by Cu2+ is the mechanism responsible for a new arrangement of the binding site of the non-heme iron leading to its more "tense" structure. Such a diamagnetic state of the non-heme iron induced by copper results in a magnetic decoupling of iron from the primary quinone acceptor. These results indicate that Cu does not cause removal of the non-heme iron from its binding site. The observed Cu2+ action on the non-heme iron and cytochrome b559 is similar to that previously observed forα-tocopherol quinone.

DOI: 10.12693/APhysPolA.109.237 PACS numbers: 82.39.Jn, 82.39.Rt, 82.50.Nd, 87.15.He, 87.64.Pj, 89.60.Fe