Membrane phosphorylation leads to the partial detachment of the chlorophyll a/b protein from photosystem II

The hypothesis that the chlorophyll fluorescence decline due to membrane phosphorylation is caused principally by the detachment and removal of LHCP from the LHCP-PS II matrix is examined. It is demonstrated that when membranes are phosphorylated in the dark (a) the fluorescence decline is greater when excited by light enriched in wavelengths absorbed mainly by LHCP (475 nm) than when excited by light absorbed to a large extent also by the PS II complex (435 nm), (b) titration with different artificial quenchers of chlorophyll fluorescence is unchanged after the phosphorylation-induced fluorescence decline, and (c) the Fv/Fm ratio does not change after the phosphorylation-induced fluorescence decline. These data indicate that it is indeed principally LHCP that interacts with the quencher (PS I presumably). This interaction involves a small fraction of the total PS II-coupled LHCP, which becomes functionally detached from the LHCP-PS II matrix.