title: Structure of photosystem II in spinach thylakoid membranes: comparison of detergent-solubilized and native complexes by electron microscopy.
abstract: 1. Electron microscopy of solubilized photosystem II (PSII) complexes and PSII in spinach thylakoid membranes has been carried out and the results have been compared with data obtained from ordered two-dimensional arrays of PSII. Membrane-bound PSII is roughly rectangular (17.6 nm x 14.1 nm) with a central stain cavity surrounded by four major lumenal domains. A comparison between the averaged projections of single (non-ordered) particles at 3.8 nm resolution and the Fourier projection maps obtained from ordered arrays (at 2-3 nm resolution) reveals close similarity and excludes the possibility that PSII observed in two-dimensional ordered arrays represents an unusual subpopulation. 2. After detergent solubilization, PSII adopts various aggregation states which were analysed by electron microscopy in conjunction with single-particle averaging. Two different types of projection of roughly rectangular shape and of dimensions 30 nm x 17 nm manifesting themselves as tetrameric sandwich structures have been revealed. This conclusion is supported by the presence of at least two axes of 2-fold rotational symmetry running perpendicular to each other and intersecting at the centre of the oligomer. Comparisons of the structures of detergent-solubilized and native PSII show that the oligomerization of PSII can be artificially induced by the process of membrane solubilization.
authors.affiliation: Department of Biochemistry and Applied Molecular Biology, UMIST, Manchester, U.K.
authors.forename: W V
authors.initials: WV
authors.lastname: Nicholson
authors.forename: F H
authors.initials: FH
authors.lastname: Shepherd
authors.forename: M F
authors.initials: MF
authors.lastname: Rosenberg
authors.forename: R C
authors.initials: RC
authors.lastname: Ford
authors.forename: A
authors.initials: A
authors.lastname: Holzenburg
mesh_terms: D002736:Chloroplasts / Q000737:chemistry / Q000648:ultrastructure; D003902:Detergents; D015394:Molecular Structure; D010316:Particle Size; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure*; D045332:Photosystem II Protein Complex; D011487:Protein Conformation; D012995:Solubility; D018724:Spinacia oleracea / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D003902:Detergents; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex