title: Crystallisation of CP43, a chlorophyll binding protein of photosystem II: an electron microscopy analysis of molecular packing.
abstract: Microcrystals of the chlorophyll binding protein, CP43, isolated from spinach thylakoid membranes have been studied by electron microscopy both in negative stain and in vitreous ice. Image analyses of three characteristic views show that the crystals are built of five different layers perpendicular to the c-axis. Each layer consists of different orientations of the CP43 protein. The unit cell derived from the end-on view (looking down the c-axis) shows an angle of 120 degrees, suggesting a threefold rotational symmetry. Both negative staining and cryo data are consistent with a hexagonal crystal lattice. Interpretation of the arrangement of the CP43 protein within this crystal lattice can be made based on 8- and 9-A electron crystallographic structures previously published that provide a model for the organisation of the transmembrane helices of CP43. Overall the analysis presented is consistent with X-ray diffraction data obtained from larger CP43 crystals and forms a framework on which to base further structural studies of this chlorophyll binding protein.
authors.affiliation: Wolfson Laboratories, Imperial College of Science, Technology and Medicine, London SW7 2AY, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Büchel
authors.forename: E
authors.initials: E
authors.lastname: Morris
authors.forename: J
authors.initials: J
authors.lastname: Barber
mesh_terms: D003460:Crystallization; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008958:Models, Molecular; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure*; D045332:Photosystem II Protein Complex; D018724:Spinacia oleracea / Q000737:chemistry
chemical_list: D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C083100:photosystem II, chlorophyll binding protein, CP-43