Changes in the efficiency of P700 photo-oxidation in response to protein phosphorylation detected by flash absorption spectroscopy

Abstract

A flash-spectroscopic study of the quantum yield of the absorption change at 820 nm due to the electron donor, P700, has been carried out with vesicles enriched in the reaction centre of photosystem one of higher plant chloroplasts. Phosphorylation of the light-harvesting chlorophyll a/b containing protein complex (LHC-2) increases the chlorophyll to P700 ratio in the vesicles by 12 % and brings about a corresponding increase in efficiency of flash-induced P700 oxidation. It is thus argued that phosphorylated LHC-2 can transfer energy directly to photosystem one and that a mobile antenna system, controlled by its reversible phosphorylation state, regulates photosynthetic electron transport.