The Action of free Radical Scavengers on Thylakoid Protein Phosphorylation and PSII Core Protein Degradation

Abstract

It was earlier shown that a 32 kDa thylakoid protein, immunodetectable by a D1/D2 antibody, is drastically reduced during thylakoid protein phosphorylation. This was observed even under low light. The reduction in immunostain coincided with the increase in the low temperature fluorescence emission ratio F730/F685, while it was fully overcome in the presence of FSBA, a kinase inhibitor (1). These results were considered to reflect an ATP-stimulation of the light-induced D1 degradation. To see which one of the PSII core proteins was mainly affected, we have utilized antibodies from a variety of sources (raised against the D-E loop of D1 from Synechocystis; against D1 of Oscillatoria chalybea and against Dl/D2). In addition, to assess whether kinase activation might be involved in this PSII core protein degradation, we have further tested the effect of various free radical scavengers (known to affect or not D1 degradation or PSII photoinactivation) on thylakoid protein phosphorylation.