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Mössbauer Studies of Cu(II) Ions Interaction with the Non-Heme Iron and Cytochrome b_{559} in a Chlamydomonas reinhardtii PSI Minus Mutant

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Burda K., Kruk J., Strzałka K., Stanek J., Schmid G., Kruse O.

Acta Physica Polonica A

2006

vol. 109

issue 3

237-247

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 b_{559} 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 Cu^{2+} 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 Cu^{2+} action on the non-heme iron and cytochrome b_{559} is similar to that previously observed forα-tocopherol quinone.

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1 Acta Physica Polonica A

1 2006

1 Burda K.

1 Kruk J.

1 Kruse O.

1 Schmid G.

1 Stanek J.

1 Strzałka K.

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Mössbauer Studies of Cu(II) Ions Interaction with the Non-Heme Iron and Cytochrome b_{559} in a Chlamydomonas reinhardtii PSI Minus Mutant