Modification of photosystem II activity by protein phosphorylation

Phosphorylation of proteins within pea thylakoid membranes decreases photosystem II (PSII) mediated electron transfer at saturating light intensities which, according to changes in room temperature chlorophyll fluorescence transients, is due to a modification in the electron transfer from QAto QB. However, a previously reported increase in the ability of DCMU to inhibit PS2 electron flow to DCPIP, as a consequence of protein phosphorylation, was not observed, although changes in DCMU efficacy were found to depend upon the redox state of the plastoquinone (PQ) pool.