The extrinsic PsbO protein modulates the oxidation/reduction rate of the exogenous Mn cation at the high-affinity Mn-binding site of Mn-depleted PSII membranes
- 184 Downloads
The oxidation of exogenous Mn(II) cations at the high-affinity (HA) Mn-binding site in Mn-depleted photosystem II (PSII) membranes with or without the presence of the extrinsic PsbO polypeptide was studied by EPR. The six-lines EPR spectrum of Mn(II) cation disappears in the absence of the PsbO protein in membranes under illumination, but there was no effect when PSII preparations bound the PsbO protein. Our study demonstrates that such effect is determined by significant influence of the PsbO protein on the ratio between the rates of Mn oxidation and reduction at the HA site when the membranes are illuminated.
KeywordsPhotosystem II PsbO extrinsic protein High-affinity Mn-binding site Mn(II) Oxygen-evolving complex
We are grateful to Prof. Yurina N.P. and Mokerova D.V. (Russian Academy of Sciences A.N. Bach Institute of Biochemistry) for performing SDS-urea-PAGE. We sincerely thank Dr. Trubitsin B.V. for help with some EPR measurements (Physical Faculty, Moscow State University) and Dr. M. Seibert (National Renewable Energy Laboratory, USA) for technical comments and correcting the English.
- Boussac A, Picaud M, Etienne A-L (1986) Effect of potassium iridic chloride on the electron donation by Mn2+ to photosystem II particles. Photobiochem Photobiophys 10:201–211Google Scholar
- Ghanotakis DF, Babckock GT, Yocum CF (1984) Structural and catalytic properties of the oxygen-evolving complex. Correlation of polypeptide and manganese release with the behavior of Z+ in chloroplasts and a highly resolved preparation of the PSII complex. Biochim Biophys Aсta 765:388–398CrossRefGoogle Scholar
- Inoue H, Wada T (1987) Requirement of manganese for electron donation of hydrogen peroxide in photosystem II reaction center complex. Plant Cell Physiol 28:767–773Google Scholar
- Porra RJ, Tompson WA, Kriedemann PE (1989) Determination of accurate extinction coefficients and simultaneous-equations for assaying chlorophyll-A and chlorophyll-B extracted with 4 different solvents - verification of the concentration of chlorophyll standards by atomic-absorption spectroscopy. Biochim Biophys Acta 975:384–394CrossRefGoogle Scholar
- Xu Q, Bricker TM (1992) Structural organization of proteins on the oxidizing side of photosystem I. Two molecules of the 33-kDa manganese-stabilizing proteins per reaction center. J Biol Chem 267:25816–25821Google Scholar