Manganese and tyrosyl radical function in photosynthetic oxygen evolution

Abstract

Photosystem II catalyzes the photosynthetic oxidation of water to O2. The structural and functional basis for this remarkable process is emerging. The catalytic site contains a tetramanganese cluster, calcium, chloride and a redox-active tyrosine organized so as to promote electroneutral hydrogen atom abstraction from manganese-bound substrate water by the tyrosyl radical. Recent work is assessed within the framework of this model for the water oxidizing process.