Biomaterial Database

Analysis of the thylakoid outer surface. Coupling factor is limited to unstacked membrane regions. 1976

K R Miller, and L A Staehelin

The structure of the spinach thylakoid outer surface has been examined by deepetching, a technique which exposes the true surfaces of biological membranes by sublimination of frozen dilute buffer. The membrane surface is covered with large (150 A average diameter) and small (90 A average diameter) particles. Approximately 30% of the large particles can be removed under conditions reported to selectively remove carboxydismutase from the membrane surface. The remaining large particles can be removed only under conditions which cause a loss of coupling factor activity. When purified coupling factor is readded to membranes from which all coupling factor activity has been removed, large particles reappear, indicating that they represent coupling factor molecules. Since the number of particles and the amount of ATPase activity in the reconstituted and control membranes were the same, coupling factor molecules may be attached to specific binding sites. Analysis of antibody labeling experiments, enzyme assays, and experiments involving the unstacking and restacking of thylakoid membranes indicate that coupling factor is excluded from regions of membrane stacking (grana) and is present only in unstacked membrane regions. The exclusion of coupling factor from grana, which are known to be centers of intense photosynthetic activity, strongly suggests that the mechanism coupling electron transport to photophosphorylation is indirect. In addition to the large and small particles, in some cases regularly spaced ridges are visible on the outer surface after unstacking. Coupling factor binding sites seem to be excluded from regions where these structures occur.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D010944	Plants	Multicellular, eukaryotic life forms of kingdom Plantae. Plants acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations. It is a non-taxonomical term most often referring to LAND PLANTS. In broad sense it includes RHODOPHYTA and GLAUCOPHYTA along with VIRIDIPLANTAE.	Plant
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002736	Chloroplasts	Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.	Chloroplast,Etioplasts,Etioplast
D005613	Freeze Etching	A replica technique in which cells are frozen to a very low temperature and cracked with a knife blade to expose the interior surfaces of the cells or cell membranes. The cracked cell surfaces are then freeze-dried to expose their constituents. The surfaces are now ready for shadowing to be viewed using an electron microscope. This method differs from freeze-fracturing in that no cryoprotectant is used and, thus, allows for the sublimation of water during the freeze-drying process to etch the surfaces.	Etching, Freeze
D005779	Immunodiffusion	Technique involving the diffusion of antigen or antibody through a semisolid medium, usually agar or agarose gel, with the result being a precipitin reaction.	Gel Diffusion Tests,Diffusion Test, Gel,Diffusion Tests, Gel,Gel Diffusion Test,Immunodiffusions,Test, Gel Diffusion,Tests, Gel Diffusion