Heptameric association of light-harvesting complex II trimers in partiallysolubilized photosystem II membranes

We report a structural characterization by electron microscopy and image an alysis of a supramolecular complex consisting of seven trimeric light-harve sting complex II proteins, The complex was readily observed in partially-so lubilized Tris-washed photosystem II membranes from spinach but was also fo und to occur, with a low frequency, in oxygen-evolving photosystem II membr anes. The structure reveals sis peripheral trimers with the same rotational orientation and a central trimer with the opposite orientation. We conclud e that the heptamer represents a naturally occurring aggregation state of p art of the light-harvesting complex II trimers in the thylakoid membranes. (C) 1999 Federation of European Biochemical Societies.