Das photosynthetische Reaktionszentrum des Purpurbakteriums <i>Rhodopseudomonas viridis</i> (Nobel‐Vortrag)

Deisenhofer, Johann; Michel, Hartmut

doi:10.1002/ange.19891010705

Cited by 117 publications

(34 citation statements)

References 81 publications

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“…Both of these residues would be expected to disrupt the transmembrane ␣-helix. In the first transmembrane protein to be studied by crystallography, the photosynthetic reaction center of Rhodopseudomonas viridis, twothirds of the tryptophan residues of the L and M subunits were located at the junction between the hydrophobic surface and the polar transition zone or in the polar regions near the hydrophobic surface (29).…”

Section: Discussionmentioning

confidence: 99%

Second-site Cleavage in Sterol Regulatory Element-binding Protein Occurs at Transmembrane Junction as Determined by Cysteine Panning

Duncan¹,

Davé²,

Sakai

et al. 1998

Journal of Biological Chemistry

137

112

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In response to sterol deprivation, two sequential proteolytic cleavages release the NH 2 -terminal fragments of sterol regulatory element-binding proteins (SREBPs) from cell membranes. The fragments translocate to the nucleus where they activate genes involved in cholesterol and fatty acid metabolism. The SREBPs are bound to membranes in a hairpin fashion. The NH 2 -terminal and COOH-terminal domains face the cytoplasm, separated by two membrane spanning segments and a short lumenal loop. The first cleavage occurs at Site-1 in the lumenal loop. The NH 2 -terminal fragment is then released by cleavage at Site-2, which is believed to lie within the first transmembrane segment. Here, we use a novel cysteine panning method to identify the second cleavage site (Site-2) in human SREBP-2 as the Leu 484 -Cys 485 bond that lies at the junction between the cytoplasmic NH 2 -terminal fragment and the first transmembrane segment. We transfected cells with cDNAs encoding fusion proteins with single cysteine residues at positions to the NH 2 -terminal and COOH-terminal sides of cysteine 485. The NH 2 -terminal fragments were tested for susceptibility to modification with N ␣ -(3-maleimidylpropionyl)biocytin, which attaches a biotin group to cysteine sulfhydryls. Cysteines to the NH 2 -terminal side of cysteine 485 were retained on the NH 2 -terminal fragment, but cysteines to the COOH-terminal side of leucine 484 were lost. Leucine 484 is three residues to the COOH-terminal side of the tetrapeptide AspArg-Ser-Arg, which immediately precedes the first transmembrane segment and is required for Site-2 cleavage.Cells maintain cholesterol homeostasis through a feedback pathway that depends upon the regulated proteolytic processing of a pair of membrane-bound transcription factors, sterol regulatory element-binding proteins-1 and -2 (SREBP-1 and SREBP-2) 1 (reviewed in Ref. 1). Cells deprived of cholesterol process the SREBPs proteolytically to release the NH 2 -terminal domains which travel to the nucleus to activate transcription of genes that regulate several metabolic pathways: uptake of cholesterol and fatty acids (low density lipoprotein receptor and lipoprotein lipase) (1, 2), synthesis of cholesterol (3-hydroxy-3-methylglutaryl-CoA reductase, 3-hydroxy-3-methylglutaryl-CoA synthase, farnesyl diphosphate synthase, squalene synthase) (1, 3-5), synthesis of fatty acids (acetyl-CoA carboxylase, fatty acid synthase, stearoyl-CoA desaturase) (1, 2, 6, 7), and synthesis of triglycerides (glycerol-3-phosphate acyltransferase) (8). When cells accumulate sterols, proteolysis of the SREBPs is suppressed, nuclear SREBPs decline, and the transcription of the target genes is reduced. This regulation assures a steady supply of cholesterol and fatty acids while preventing their overaccumulation.SREBPs are unique among transcription factors because they are synthesized as membrane-bound precursors with three domains. The precursors are bound to the endoplasmic reticulum and nuclear envelope in a hairpin orientation (9). The cytoplasmic NH 2...

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Section: Discussionmentioning

confidence: 99%

Second-site Cleavage in Sterol Regulatory Element-binding Protein Occurs at Transmembrane Junction as Determined by Cysteine Panning

Duncan¹,

Davé²,

Sakai

et al. 1998

Journal of Biological Chemistry

137

112

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“…Finally, 7 was coupled to the silicon phthalocyanine core in the presence of K 2 CO 3 to produce the dendrimer G2 with four fullerene subunits in 62 % yield. 1 H and 13 C NMR spectra were most useful for the characterization of G2. In spite of the increase in generation number, well-resolved resonance signals in the aliphatic and aromatic regions were present in both the 1 H and 13 C NMR spectra of G2, and distinct assignments could be made for the structure of G2 (see the Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

“…These observations suggest the quenching of 1 SiPc* by the appended C 60 entities. The quenching is likely to occur by the charge-separation process via 1 SiPc* generating SiPcC…”

Section: Cyclic Voltammetry Studiesmentioning

confidence: 99%

“…Photophysical properties of newly synthesized SiPc-n C 60 have been investigated by time-resolved fluorescence and transient absorption analysis with pulsed laser light. Laser photolysis measurements suggest the occurrence of a charge-separation process from 1 SiPc* to the C 60 subunits. The nanosecond transient absorption spectra in the near-IR region indicate that the lifetimes of the formed radical ion pairs are prolonged on the order of SiPc-8 C 60 > SiPc-4 C 60 > SiPc-2 C 60 , which may be related to the electron migration among the C 60 subunits.…”

Section: Introductionmentioning

confidence: 97%

“…[1] Various strategies have been employed to develop molecular electronic devices that use porphyrin arrays linked by covalent bonds, [2] self-assemblies, [3] dendrimers, [4] or polymers. [5] Phthalocyanines (Pc), structural analogues of porphyrins, with a strong absorption in the visible region (the Q band; l max % 700 nm), are highly versatile and stable chromophores with unique photophysical and photochemical properties that make them, alone or in combination with many other electro-and photoactive moieties, ideal building blocks for the construction of molecular materials with special electronic and optical properties.…”

Section: Introductionmentioning

confidence: 99%

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Silicon‐Phthalocyanine‐Cored Fullerene Dendrimers: Synthesis and Prolonged Charge‐Separated States with Dendrimer Generations

Elkhouly¹,

Kang²,

Kay³

et al. 2007

Chemistry A European J

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Silicon-phthalocyanine-cored fullerodendrimers with up to eight fullerene substituents (SiPc-n C(60); n=2, 4, and 8) have been synthesized. Photophysical properties of newly synthesized SiPc-n C(60) have been investigated by time-resolved fluorescence and transient absorption analysis with pulsed laser light. Laser photolysis measurements suggest the occurrence of a charge-separation process from (1)SiPc* to the C(60) subunits. The nanosecond transient absorption spectra in the near-IR region indicate that the lifetimes of the formed radical ion pairs are prolonged on the order of SiPc-8 C(60)>SiPc-4 C(60)>SiPc-2 C(60), which may be related to the electron migration among the C(60) subunits. The usefulness of SiPc-n C(60) as light-harvesting systems, evaluated as a ratio of the rates of charge recombination to those of charge separation, increases markedly with the dendrimer generation.

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Künstliche Photosynthese: Nachahmung der Redoxasymmetrie

Benniston

Mackie

Harriman³

1998

Angewandte Chemie

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Ein richtungsabhängiger, lichtinduzierter Elektronentransfer findet im rechts schematisch dargestellten Catenan statt. Es ähnelt dem photosynthetischen Reaktionszentrum, da die beiden chemisch identischen, an einen Rutheniumkomplex als Donor gebundenen Acceptoren (Rechtecke) wegen ihrer unterschiedlich polaren Umgebung verschiedene Reduktionspotentiale haben. Die Elektronenübertragung erfolgt bevorzugt (zu 85%) auf den nicht umhüllten Acceptor.

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Das photosynthetische Reaktionszentrum des Purpurbakteriums Rhodopseudomonas viridis (Nobel‐Vortrag)

Cited by 117 publications

References 81 publications

Second-site Cleavage in Sterol Regulatory Element-binding Protein Occurs at Transmembrane Junction as Determined by Cysteine Panning

Second-site Cleavage in Sterol Regulatory Element-binding Protein Occurs at Transmembrane Junction as Determined by Cysteine Panning

Silicon‐Phthalocyanine‐Cored Fullerene Dendrimers: Synthesis and Prolonged Charge‐Separated States with Dendrimer Generations

Künstliche Photosynthese: Nachahmung der Redoxasymmetrie

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