High light induced increase in PSII phosphorylation and its effect on MgCl2–dependence of thylakoid membrane light scattering.

A, thylakoid membrane proteins from wild type plants adapted to dark, or exposed to normal or high light for 3 hours were separated on SDS-PAGE and immunoblotted with anti-phosphothreonine antibody from Zymed laboratories. The samples were loaded at three different chlorophyll concentrations, as indicated. Positions of the phosphorylated thylakoid proteins and of the molecular mass markers are indicated. B, titration of the light-scattering changes in thylakoid membranes from the leaves exposed to normal or high light, as indicated, using 0, 5, 10, 15, 20 and 30 mM MgCl2 and normalization of absorbance at 580 nm to the 678 nm signals. Error bars represent S.D. of at least three independent experiments.