Correlation of the cytochrome c550 content of cyanobacterial Photosystem II with the EPR properties of the oxygen-evolving complex

K. V. Lakshmi, Michael J. Reifler, Dexter A. Chisholm, Jamie Y. Wang, Bruce A. Diner, Gary W. Brudvig

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29 Citations (Scopus)


The Mn4 cluster of PS II advances through a series of oxidation states (S states) that catalyze the breakdown of water to dioxygen in the oxygen-evolving complex. The present study describes the engineering and purification of highly active PS II complexes from mesophilic His-tagged Synechocystis PCC 6803 and purification of PS II core complexes from thermophilic wild-type Synechococcus lividus with high levels of the extrinsic polypeptide, cytochrome c550. The g = 4.1 S2 state EPR signal, previously not characterized in untreated cyanobacterial PS II, is detected in high yields in these PS II preparations. We present a complete characterization of the g = 4.1 state in cyanobacterial His-tagged synechocystis PCC 6803 PS II and S. lividus PS II. Also presented are a determination of the stoichiometry of cytochrome c550 bound to His-tagged Synechocystis PCC 6803 PS II and analytical ultracentrifugation results which indicate that cytochrome c550 is a monomer in solution. The temperature-dependent multiline to g = 4.1 EPR signal conversion observed for the S2 state in cyanobacterial PS II with high cytochrome c550 content is very similar to that previously found for spinach PS II. In spinach PS II, the formation of the S2 state g = 4.1 EPR signal has been found to correlate with the binding of the extrinsic 17 and 23 kDa polypeptides. The finding of a similar correlation in cyanobacterial PS II with the binding of cytochrome c550 suggests a functional homology between cytochrome c550 and the 17 and 23 kDa extrinsic proteins of spinach PS II.

Original languageEnglish
Pages (from-to)175-189
Number of pages15
JournalPhotosynthesis Research
Issue number2
Publication statusPublished - 2002


  • Cytochrome c
  • EPR spectroscopy
  • Metal-affinity chromatography
  • Oxygen-evolving complex
  • Photosystem II
  • Synechocystis PCC 6803

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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