Biomaterial Database

Spatial organization of the cytochrome b6-f complex within chloroplast thylakoid membranes. 1986

D R Allred, and L A Staehelin

The spatial distribution of the chloroplast thylakoid protein complex comprised of cytochromes f and b-563, and the Rieske iron-sulfur protein (Cyt b6-f) has been controversial because of conflicting results obtained by different techniques. We have combined the following biochemical and immunochemical techniques to approach this question: (1) French press disruption of thylakoids, followed by repeated two-phase aqueous polymer partitioning to separate inside-out grana from right-side-out stroma membrane fragments; (2) electrophoretic analysis followed by the 3,3',5,5'-tetramethylbenzidine stain for cytochrome hemes; (3) electroblot analysis with anti-Cyt b6-f antibodies; (4) agglutination of membrane fragments with anti-Cyt b6-f antibodies; and (5) post-embedment thin-section immunolabeling of chemically fixed or ultrarapidly frozen chloroplasts with anti-Cyt b6-f antibodies. Our results indicate that the complex is present in both of the isolated membrane fragment populations in similar amounts, with the bulk of the immunoreactive sites exposed to the thylakoidal lumen. Direct immunolabeling of thin-sectioned chloroplasts resulted in localization of the complex throughout the thylakoids, without specialized compartmentation. These results provide both the temporal and spatial resolution necessary for accurate localization of the complex. We concur with models proposing distribution of Cyt b6-f throughout all thylakoid membranes.

UI	MeSH Term	Description	Entries
D007425	Intracellular Membranes	Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.	Membranes, Intracellular,Intracellular Membrane,Membrane, Intracellular
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
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
D003573	Cytochrome b Group	Cytochromes (electron-transporting proteins) with protoheme (HEME B) as the prosthetic group.	Cytochromes Type b,Cytochromes, Heme b,Group, Cytochrome b,Heme b Cytochromes,Type b, Cytochromes,b Cytochromes, Heme,b Group, Cytochrome
D003580	Cytochromes	Hemeproteins whose characteristic mode of action involves transfer of reducing equivalents which are associated with a reversible change in oxidation state of the prosthetic group. Formally, this redox change involves a single-electron, reversible equilibrium between the Fe(II) and Fe(III) states of the central iron atom (From Enzyme Nomenclature, 1992, p539). The various cytochrome subclasses are organized by the type of HEME and by the wavelength range of their reduced alpha-absorption bands.	Cytochrome
D005614	Freeze Fracturing	Preparation for electron microscopy of minute replicas of exposed surfaces of the cell which have been ruptured in the frozen state. The specimen is frozen, then cleaved under high vacuum at the same temperature. The exposed surface is shadowed with carbon and platinum and coated with carbon to obtain a carbon replica.	Fracturing, Freeze,Fracturings, Freeze,Freeze Fracturings
D013045	Species Specificity	The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.	Species Specificities,Specificities, Species,Specificity, Species
D045346	Cytochrome b6f Complex	A protein complex that includes CYTOCHROME B6 and CYTOCHROME F. It is found in the THYLAKOID MEMBRANE and plays an important role in process of PHOTOSYNTHESIS by transferring electrons from PLASTOQUINONE to PLASTOCYANIN or CYTOCHROME C6. The transfer of electrons is coupled to the transport of PROTONS across the membrane.	Cytochrome b(6)-f Complex,Cytochrome b6-f,Cytochrome b6f,Cytochrome bf,Cytochrome bf Complex,Cytochrome b6 f
D045348	Cytochromes f	Cytochromes f are found as components of the CYTOCHROME B6F COMPLEX. They play important role in the transfer of electrons from PHOTOSYSTEM I to PHOTOSYSTEM II.	Cytochrome f,Apocytochrome f