ABSTRACT
The light-harvesting chlorophyll a/b protein complex of photosystem II (LHC II) is the main antenna capturing solar energy in the chloroplasts of green plants and in green algae. LHC II, a trimeric integral membrane chlorophyll protein complex from the photosynthetic membrane of plant chloroplasts, can be crystallized from NG solution by vapor diffusion using methods similar to those developed for crystallizing bacteriorhodopsin, the bacterial reaction centre complex from Rhodopseudomonas viridis and matrix porin. LHC II binds most of the chlorophyll b (Chl b) in plants, containing an almost equal number of Chl a and Chl b molecules, whereas the majority of the other Chl protein complexes of green plants contain only Chl a. The structure analysis of two- and thin three-dimensional crystals of LHC II has shown that the complex is a trimer, consisting of three protein monomers related by threefold symmetry. Isolated, detergent-solubilized LHC II was fractionated by ion-exchange column chromatography.
