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111.
Kühn-Wache K Bär JW Hoffmann T Wolf R Rahfeld JU Demuth HU 《Biological chemistry》2011,392(3):223-231
Dipeptidyl peptidase 4/CD26 (DP4) is a multifunctional serine protease liberating dipeptide from the N-terminus of (oligo)peptides which can modulate the activity of these peptides. The enzyme is involved in physiological processes such as blood glucose homeostasis and immune response. DP4 substrate specificity is characterized in detail using synthetic dipeptide derivatives. The specificity constant k(cat)/K(m) strongly depends on the amino acid in P?-position for proline, alanine, glycine and serine with 5.0 x 10? M?1 s?1, 1.8 x 10? M?1 s?1, 3.6 x 102 M?1 s?1, 1.1 x 102 M?1 s?1, respectively. By contrast, kinetic investigation of larger peptide substrates yields a different pattern. The specific activity of DP4 for neuropeptide Y (NPY) cleavage comprising a proline in P?-position is the same range as the k(cat)/K(m) values of NPY derivatives containing alanine or serine in P?-position with 4 x 10? M?1 s?1, 9.5 x 10? M?1 s?1 and 2.1 x 10? M?1 s?1, respectively. The proposed existence of an additional binding region outside the catalytic center is supported by measurements of peptide substrates with extended chain length. This 'secondary' binding site interaction depends on the amino acid sequence in P?'-P?'-position. Interactions with this binding site could be specifically blocked for substrates of the GRF/glucagon peptide family. By contrast, substrates not belonging to this peptide family and dipeptide derivative substrates that only bind to the catalytic center of DP4 were not inhibited. This more selective inhibition approach allows, for the first time, to distinguish between substrate families by substrate-discriminating inhibitors. 相似文献
112.
Franziska Todt Zeynep Cakir Frank Reichenbach Frederic Emschermann Joachim Lauterwasser Andrea Kaiser Gabriel Ichim Stephen WG Tait Stephan Frank Harald F Langer Frank Edlich 《The EMBO journal》2015,34(1):67-80
The Bcl-2 proteins Bax and Bak can permeabilize the outer mitochondrial membrane and commit cells to apoptosis. Pro-survival Bcl-2 proteins control Bax by constant retrotranslocation into the cytosol of healthy cells. The stabilization of cytosolic Bax raises the question whether the functionally redundant but largely mitochondrial Bak shares this level of regulation. Here we report that Bak is retrotranslocated from the mitochondria by pro-survival Bcl-2 proteins. Bak is present in the cytosol of human cells and tissues, but low shuttling rates cause predominant mitochondrial Bak localization. Interchanging the membrane anchors of Bax and Bak reverses their subcellular localization compared to the wild-type proteins. Strikingly, the reduction of Bax shuttling to the level of Bak retrotranslocation results in full Bax toxicity even in absence of apoptosis induction. Thus, fast Bax retrotranslocation is required to protect cells from commitment to programmed death. 相似文献
113.
The chaperonin TRiC controls polyglutamine aggregation and toxicity through subunit-specific interactions 总被引:1,自引:0,他引:1
Misfolding and aggregation of proteins containing expanded polyglutamine repeats underlie Huntington's disease and other neurodegenerative disorders. Here, we show that the hetero-oligomeric chaperonin TRiC (also known as CCT) physically interacts with polyglutamine-expanded variants of huntingtin (Htt) and effectively inhibits their aggregation. Depletion of TRiC enhances polyglutamine aggregation in yeast and mammalian cells. Conversely, overexpression of a single TRiC subunit, CCT1, is sufficient to remodel Htt-aggregate morphology in vivo and in vitro, and reduces Htt-induced toxicity in neuronal cells. Because TRiC acts during de novo protein biogenesis, this chaperonin may have an early role preventing Htt access to pathogenic conformations. Based on the specificity of the Htt-CCT1 interaction, the CCT1 substrate-binding domain may provide a versatile scaffold for therapeutic inhibitors of neurodegenerative disease. 相似文献
114.
115.
Lewis EC Blaabjerg L Størling J Ronn SG Mascagni P Dinarello CA Mandrup-Poulsen T 《Molecular medicine (Cambridge, Mass.)》2011,17(5-6):369-377
In type 1 diabetes, inflammatory and immunocompetent cells enter the islet and produce proinflammatory cytokines such as interleukin-1β (IL-1β), IL-12, tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ); each contribute to β-cell destruction, mediated in part by nitric oxide. Inhibitors of histone deacetylases (HDAC) are used commonly in humans but also possess antiinflammatory and cytokine-suppressing properties. Here we show that oral administration of the HDAC inhibitor ITF2357 to mice normalized streptozotocin (STZ)-induced hyperglycemia at the clinically relevant doses of 1.25-2.5 mg/kg. Serum nitrite levels returned to nondiabetic values, islet function improved and glucose clearance increased from 14% (STZ) to 50% (STZ + ITF2357). In vitro, at 25 and 250 nmol/L, ITF2357 increased islet cell viability, enhanced insulin secretion, inhibited MIP-1α and MIP-2 release, reduced nitric oxide production and decreased apoptosis rates from 14.3% (vehicle) to 2.6% (ITF2357). Inducible nitric oxide synthase (iNOS) levels decreased in association with reduced islet-derived nitrite levels. In peritoneal macrophages and splenocytes, ITF2357 inhibited the production of nitrite, as well as that of TNFα and IFNγ at an IC(50) of 25-50 nmol/L. In the insulin-producing INS cells challenged with the combination of IL-1β plus IFNγ, apoptosis was reduced by 50% (P < 0.01). Thus at clinically relevant doses, the orally active HDAC inhibitor ITF2357 favors β-cell survival during inflammatory conditions. 相似文献
116.
Stefanie Wagner Frédéric Lagane Andaine Seguin‐Orlando Mikkel Schubert Thibault Leroy Erwan Guichoux Emilie Chancerel Inger Bech‐Hebelstrup Vincent Bernard Cyrille Billard Yves Billaud Matthias Bolliger Christophe Croutsch Katarina Čufar Frédérique Eynaud Karl Uwe Heussner Joachim Köninger Fabien Langenegger Frédéric Leroy Christine Lima Nicoletta Martinelli Garry Momber André Billamboz Oliver Nelle Antoni Palomo Raquel Piqué Marianne Ramstein Roswitha Schweichel Harald Stäuble Willy Tegel Xavier Terradas Florence Verdin Christophe Plomion Antoine Kremer Ludovic Orlando 《Molecular ecology》2018,27(5):1138-1154
Reconstructing the colonization and demographic dynamics that gave rise to extant forests is essential to forecasts of forest responses to environmental changes. Classical approaches to map how population of trees changed through space and time largely rely on pollen distribution patterns, with only a limited number of studies exploiting DNA molecules preserved in wooden tree archaeological and subfossil remains. Here, we advance such analyses by applying high‐throughput (HTS) DNA sequencing to wood archaeological and subfossil material for the first time, using a comprehensive sample of 167 European white oak waterlogged remains spanning a large temporal (from 550 to 9,800 years) and geographical range across Europe. The successful characterization of the endogenous DNA and exogenous microbial DNA of 140 (~83%) samples helped the identification of environmental conditions favouring long‐term DNA preservation in wood remains, and started to unveil the first trends in the DNA decay process in wood material. Additionally, the maternally inherited chloroplast haplotypes of 21 samples from three periods of forest human‐induced use (Neolithic, Bronze Age and Middle Ages) were found to be consistent with those of modern populations growing in the same geographic areas. Our work paves the way for further studies aiming at using ancient DNA preserved in wood to reconstruct the micro‐evolutionary response of trees to climate change and human forest management. 相似文献
117.
Theiss C Schmitt FJ Pieper J Nganou C Grehn M Vitali M Olliges R Eichler HJ Eckert HJ 《Journal of plant physiology》2011,168(12):1473-1487
The cyanobacterium Acaryochloris marina is unique because it mainly contains Chlorophyll d (Chl d) in the core complexes of PS I and PS II instead of the usually dominant Chl a. Furthermore, its light harvesting system has a structure also different from other cyanobacteria. It has both, a membrane-internal chlorophyll containing antenna and a membrane-external phycobiliprotein (PBP) complex. The first one binds Chl d and is structurally analogous to CP43. The latter one has a rod-like structure consisting of three phycocyanin (PC) homohexamers and one heterohexamer containing PC and allophycocyanin (APC). In this paper, we give an overview on the investigations of excitation energy transfer (EET) in this PBP-light-harvesting system and of charge separation in the photosystem II (PS II) reaction center of A. marina performed at the Technische Universität Berlin. Due to the unique structure of the PBP antenna in A. marina, this EET occurs on a much shorter overall time scale than in other cyanobacteria. We also briefly discuss the question of the pigment composition in the reaction center (RC) of PS II and the nature of the primary donor of the PS II RC. 相似文献
118.
The aim of this study was to establish a new tool for screening surface displayed peptide libraries based on the idea that cells expressing an enzyme inhibitor at the surface can be specifically labeled by the target enzyme. For this purpose peptide P15, exhibiting a K(i) value of 0.25 microM toward human cathepsin G, was expressed on the Escherichia coli cell surface by the use of Autodisplay. Purified cathepsin G was coupled to biotin and incubated with cells expressing the inhibitor. After addition of streptavidin-fluorescein isothiocyanate, these cells could be clearly differentiated from control cells by whole-cell fluorescence using flow cytometer analysis. To determine whether this protocol can be used for the sorting of single cells, a mixed population of cells with and without inhibitor was treated accordingly. Single cells were selected by increased fluorescence and sorted using fluorescence-activated cell sorting (FACS). Single cell clones were obtained and subjected to DNA sequence analysis. It turned out that the bacteria selected by this protocol displayed the correct peptide inhibitor at the cell surface. The protocol was then used to screen random peptide libraries, expressed at the cell surface, and a new lead structure for human cathepsin G (IC50 = 11.7 microM) was identified. The new drug discovery tool presented here consists of three steps: (a) surface display of peptide libraries, (b) selection of single cells with inhibiting structures by using the inherent affinity of the target enzyme, and (c) sorting of single cells, which were labeled by FACS. 相似文献
119.
120.
Summary The modern hadromerid coralline spongeSpirastrella (Acanthochaetetes) wellsi exhibits a unique secondary high-Mg calcite (>19 mol % MgCO3) basal skeleton. The basal skeleton is constructed of bundles of elongated crystals more or less tangentially orientated.
The initial formation of these crystals is controlled by soluble highly acidic aspartic and glutamic-rich (40%) macromolecules.
The skeletal mineralization occurs in four different loci: in the top of the calicles, at the tabulae, on collagenous anchor
fibres, and within closed spaces between the tabulae. The clicle walls are formed on the uppermost top of the basal skeleton
as a continuous process. Based on long term stainings with Ca2+-chelating fluorochroms (calcein, chlorotetracyclines) the growth rate of this sponge is extremely low with ca. 50–100μm/a.
The skeletal formation takes places outside the sponge, within a narrow zone (300–500 nm) between the basopinacoderm and the
mature basal skeleton. The sponge produces thread-like folded templates (‘spaghetti fibres’) of 0,5–2 μm size, the shape controlling
insoluble organic matrix. These templates become mineralized in a first step as MgCO3, then are stretched. A soluble organic matrix is also secreted, and remains are included inside the mineralized skeleton.
This organic matrix consists of in a complex mixture containing small very acidic proteins (5, 13, 31 KD; 40% Asp and Glu
and therefore most probably Ca2+-binding) and high molecular weight glycoproteins among several other organic compounds. The mature crystals are high-Mg calcites.
During calcification large cells with large reserve granules (LCG) are always present in a tight connection with the basopinacoderm.
These cells form also the collagenous anchor fibres. Primary tabulae are formed by a non-collagenous organic sheet. Calcification
happens only when LCG cells are enriched on the organic sheet. Randomly oriented high-Mg calcite crystals are growing on the
collagenous anchor fibres. The same type of the mineralization is observed within the spaces of the tabulae. This particular
case of mineralization is controlled by decaying sponge tissue (ammonification). The δ13C values are in equilibrium with the ambient sea water and vary between +3.2 and +2.8 ‰. The mode of mineralization of the
basal skeleton can be described as biologically induced resp. matrix mediated. 相似文献