Modification of the chloride requirement for photosynthetic O₂ evolution

Abstract

In thylakoid preparations from spinach and the halophyte Avicennia marina a correlation is observed between functional O 2 evolution at low chloride concentrations and the presence of the 23 kDa protein. Addition of spinach 23 kDa protein to polypeptide‐depleted halophyte inside‐out thylakoid vesicles lowers their chloride requirement for optimal O 2 evolution activity from 250 to 5 mM. It is suggested that the specific role for the 23 kDa protein is to increase the affinity of the water oxidation site for chloride.