Does photoinhibition and/or phosphorylation of photosystem II influence its in vivo oligomeric state?

We have examined the effects of phosphorylation and photoinhibition upon grana membranes and photosystem II (PSII) by electron microscopy and single particle analysis. No change to the overall size of PSII complexes was observed after photoinhibition. PSII centres were found to be in closer proximity to each other after phosphorylation, an effect which was reversed by photoinhibition. There were also distinct changes to thylakoid sensitivity to detergent with a reduction in (detergent-insensitive) grana membrane by up to 40% after phosphorylation and/or photoinhibition. Only minor changes to the shape and domain architecture of PSII were apparent after photoinhibition. Our data argue against the recently proposed hypothesis that photoinhibition causes a change to the oligomeric form of the complex. Copyright (C) 1999 Elsevier Science B.V.