The release of polypeptides and manganese from oxygen-evolving photosystem II preparations following zinc-treatment |
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Affiliation: | Institute of Biochemistry, Odense University, Campusvej 55, 5230 Odense M, Denmark |
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Abstract: | Inhibition of oxygen evolution in photosystem II membrane fragments from pea chloroplasts by washing with Zn2+ causes appearance of the EPR signal of Mn(H2O)62+. This Mn2+ remains associated with the membrane fraction. Release of Mn2+ into the medium was correlated with the amount of the 23 kDa protein removed from the membrane. This suggests that this protein may function as a ‘gate’ to an aqueous compartment into which Mn2+ is released. Inhibition by Zn2+ correlated with the release of 1 Mn2+ per reaction centre, out of a total stoichiometry of 4 Mn atoms per reaction centre. By comparing the release of Mn following Zn-treatment of NaCI or CaC12 washed membranes, it is concluded that the 33 kDa protein is involved in binding of 2 Mn. |
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