Minimal Mn requirement for functional water splitting in photosystem II

Abstract

The possibility for heterogeneous metal replacement (Klimov, V.V. et al, 1982, FEBS Letts, 148, 307-312) in the Mn containing catalytic site of photosystem II (PSII) has been explored. Spinach plants were grown hydroponically in a minimal Mn environment supplemented with additional transition metals in the growth medium. Conditions were found in which the plants grow successfully and exhibit control levels of O2 evolution activity (400 m mol O2 /mg Chl/hr). The Mn ion content of the material grown in the minimal Mn environment, corresponds to 2.0 ± 0.4 Mn ions per reactions centre (200 Chl) compared to 4.1 ± 0.4 for the control PSII samples. EPR characterisation of this material is underway and will be reported.