Photosystem II catalyzes the light-driven oxidation of water and hence provides the electrons and protons needed for subsequent carbon fixation. As a by-product oxygen is produced. This process, which takes place at the oxygen evolving complex is strictly dependent on the manganese (Mn) cluster. Hence the formation of the inorganic Mn cluster is essential for plant growth and development. We identified a protein, PAM71, that is crucial for this process. The knockout mutant pam71 was shown to be impaired in delivery of manganese across the thylakoid membrane into the thylakoid lumen. As a consequence, the mutant plants were affected in photosystem II efficiency. Like other photosystem II mutants, pam71 has pale-green leaves and impaired growth. Our current model is that PAM71 acts as a Mn2+/proton exchanger.
Image: Photosystem II efficiency is strongly reduced as determinedby Fv/Fm analysis in pam71 mutant plants
PAM71 presumably acts as a Mn2+/H+ exchanger
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