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151.
Neuronal death after brain injury 总被引:6,自引:0,他引:6
152.
To monitor functionally important metal ions and possible cross talk in RNase P RNA mediated cleavage we studied cleavage of substrates, where the 2′OH at the RNase P cleavage site (at −1) and/or at position +73 had been replaced with a 2′ amino group (or 2′H). Our data showed that the presence of 2′ modifications at these positions affected cleavage site recognition, ground state binding of substrate and/or rate of cleavage. Cleavage of 2′ amino substituted substrates at different pH showed that substitution of Mg2+ by Mn2+ (or Ca2+), identity of residues at and near the cleavage site, and addition of C5 protein influenced the frequency of miscleavage at −1 (cleavage at the correct site is referred to as +1). From this we infer that these findings point at effects mediated by protonation/deprotonation of the 2′ amino group, i.e. an altered charge distribution, at the site of cleavage. Moreover, our data suggested that the structural architecture of the interaction between the 3′ end of the substrate and RNase P RNA influence the charge distribution at the cleavage site as well as the rate of cleavage under conditions where the chemistry is suggested to be rate limiting. Thus, these data provide evidence for cross talk between the +73/294 interaction and the cleavage site in RNase P RNA mediated cleavage. We discuss the role metal ions might play in this cross talk and the likelihood that at least one functionally important metal ion is positioned in the vicinity of, and use the 2′OH at the cleavage site as an inner or outer sphere ligand. 相似文献
153.
Line?NybakkenEmail author Wolfgang?Bilger Ulf?Johanson Lars?Olof?Bj?rn Mathias?Zielke Bj?rn?Solheim 《Polar Biology》2004,27(7):383-390
Stratospheric ozone depletion is most pronounced at high latitudes, and the concurring increased UV-B radiation might adversely affect plants from polar areas. However, vascular plants may protect themselves against UV-B radiation by UV-absorbing compounds located in the epidermis. In this 3-year study, epidermal UV-B (max 314 nm) and UV-A (max 366 nm) screening was assessed using a fluorescence method in 12 vascular species growing in their natural environment at Svalbard. The potential for acclimation to increased radiation was studied with artificially increased UV-B, simulating 11% ozone depletion. Open-top chambers simulated an increase in temperature of 2–3°C in addition to the UV-B manipulation. Adaxial epidermal UV-B transmittance varied between 1.6 and 11.4%. Artificially increased UV-B radiation and temperature did not consistently influence the epidermal UV-B transmittance in any of the measured species, suggesting that they may not have the potential to increase their epidermal screening, or that the screening is already high enough at the applied UV-B level. We propose that environmental factors other than UV-B radiation may influence epidermal UV-B screening. 相似文献
154.
Bultreys A Gheysen I Wathelet B Schäfer M Budzikiewicz H 《Zeitschrift für Naturforschung. C, Journal of biosciences》2004,59(9-10):613-618
The structure elucidation of the cyclic (lactonic) forms of the pyoverdins with a succinamide side chain originally produced by the closely related species Pseudomonas syringae and P. cichorii is reported. Mass spectrometry and nuclear magnetic resonance analyses as well as the determination of the configuration of the amino acids after degradation indicate that these two pyoverdins differ only by the replacement of the first in-chain serine by glycine. The pyoverdins of P. syringae and P. cichorii and the dihydropyoverdin of P. syringae can be used by both species as siderophores. 相似文献
155.
Zeidler M Zhou Q Sarda X Yau CP Chua NH 《The Plant journal : for cell and molecular biology》2004,40(3):355-365
Plants use the family of phytochrome photoreceptors to sense their light environment in the red/far-red region of the spectrum. Phytochrome A (phyA) is the primary photoreceptor that regulates germination and early seedling development. This phytochrome mediates seedling de-etiolation for the developmental transition from heterotrophic to photoauxotrophic growth. High intensity far-red light provides a way to specifically assess the role of phyA in this process and was used to isolate phyA-signaling intermediates. fhy1 and pat3 (renamed fhy1-3) are independently isolated alleles of a gene encoding a phyA signal transduction component. FHY1 is a small 24 kDa protein that shows no homology to known functional motifs, besides a small conserved septin-related domain at the C-terminus, a putative nuclear localization signal (NLS) and a putative nuclear exclusion signal (NES). Here we demonstrate that the septin-related domain is important for FHY1 to transmit phyA signals. Moreover, the putative NLS and NES of FHY1 are indeed involved in its nuclear localization and exclusion. Nuclear localization of FHY1 is needed for it to execute responses downstream of phyA. Together with the results from global expression analysis, our findings point to an important role of FHY1 in phyA signaling through its nuclear translocation and induction of gene expression. 相似文献
156.
The human intercellular adhesion molecule gene (ICAM) cluster is located in a GC-rich and gene-rich region on HSA 19p13.2. We determined the complete DNA sequence of a 185-kb porcine bacterial artificial chromosome (BAC) clone containing parts of the ICAM gene cluster. We used the porcine sequence for a detailed comparative analysis between human, pig, mouse and rat. The 185 kb of porcine sequence covered 220 kb of homologous sequence in the human genome, which adds to the growing evidence that the porcine genome is somewhat smaller than the human genome. The genomic sequences of the four species showed a high level of conserved synteny and no rearrangements in gene order were observed. During evolution, the ICAM3 gene was inactivated by mutation in the mouse and rat genome, whereas it is still present in the human and pig genome. The loss of Icam3 in rodent genomes might be relevant for rodent-specific properties of the T-cell-mediated immune response. All the other investigated genes are conserved across all four investigated sequences. 相似文献
157.
Cytoplasmic Ca(2+) ([Ca(2+)](i)) and membrane potential changes were measured in clonal pancreatic beta cells using a fluorimetric imaging plate reader (FLIPR). KCl (30 mM) produced a fast membrane depolarization immediately followed by increase of [Ca(2+)](i) in BRIN-BD11 cells. l-Alanine (10 mM) but not l-arginine (10 mM) mimicked the KCl profile and also produced a fast membrane depolarization and elevation of [Ca(2+)](i). Conversely, a rise in glucose from 5.6 mM to 11.1 or 16.7 mM induced rapid membrane depolarization, followed by a slower and delayed increase of [Ca(2+)](i). GLP-1 (20 nM) did not affect membrane potential or [Ca(2+)](i). In contrast, acetylcholine (ACh, 100 microM) induced fast membrane depolarization immediately followed by a modest [Ca(2+)](i) increase. When extracellular Ca(2+) was buffered with EGTA, ACh mobilized intracellular calcium stores and the [Ca(2+)](i) increase was reduced by 2-aminoethoxydiphenyl borate but not by dantrolene, indicating the involvement of inositol triphosphate receptors (InsP(3)R). It is concluded that membrane depolarization of beta cells by glucose stimulation is not immediately followed by elevation of [Ca(2+)](i) and other metabolic events are involved in glucose induced stimulus-secretion coupling. It is also suggested that ACh mobilizes intracellular Ca(2+) through store operated InsP(3)R. 相似文献
158.
Deigweiher K Drell TL Prutsch A Scheidig AJ Lübben M 《Journal of bioenergetics and biomembranes》2004,36(1):151-159
The P-type CPX-ATPases are responsible for the transport of heavy metal ions in archaea, bacteria, and eukaryotes. We have chosen one of the two CPX-ATPases of the thermophile Sulfolobus solfataricus, CopB (= SSO2896) for the investigation of the molecular mechanism of this integral membrane protein. We recombinately expressed three different soluble domains of this protein (named CopB-A, CopB-B, and CopB-C) in Escherichia coli and purified them to homogeneity. 3D crystals of CopB-B, the 29 kDa catalytic ATP binding/phosphorylation domain were produced, which diffracted to a resolution of 2.2 A. CopB-B has heavy metal stimulated phosphatase activity, which was half maximal in the presence of 80 microM Cu2+. The protein forms a phosphorylated intermediate with the substrate gamma-(32P)-ATP. No specific activation of the polypeptide was observed, when CopB-B phosphatase activity was tested in the presence of the purified CopB-C and CopB-A proteins, which provide the cation binding and the phosphatase domains. We conclude that CopB is a putatively copper translocating ATPase, in which structural elements integrally located in the membrane are required for full, coordinated activation of the catalytic ATP binding domain. 相似文献
159.
The development of potent non-peptidic PTP-1B inhibitors 总被引:2,自引:0,他引:2
Dufresne C Roy P Wang Z Asante-Appiah E Cromlish W Boie Y Forghani F Desmarais S Wang Q Skorey K Waddleton D Ramachandran C Kennedy BP Xu L Gordon R Chan CC Leblanc Y 《Bioorganic & medicinal chemistry letters》2004,14(4):1039-1042
The SAR from our peptide libraries was exploited to design a series of potent deoxybenzoin PTP-1B inhibitors. The introduction of an ortho bromo substituent next to the difluoromethylphosphonate warhead gave up to 20-fold increase in potency compared to the desbromo analogues. In addition, these compounds were orally bioavailable and active in the animal models of non-insulin dependent diabetes mellitus (NIDDM). 相似文献
160.
Hangeland JJ Doweyko AM Dejneka T Friends TJ Devasthale P Mellström K Sandberg J Grynfarb M Sack JS Einspahr H Färnegårdh M Husman B Ljunggren J Koehler K Sheppard C Malm J Ryono DE 《Bioorganic & medicinal chemistry letters》2004,14(13):3549-3553
A set of thyromimetics having improved selectivity for TR-beta1 were prepared by replacing the 3'-isopropyl group of 2 and 3 with substituents having increased steric bulk. From this limited SAR study, the most potent and selective compounds identified were derived from 2 and contained a 3'-phenyl moiety bearing small hydrophobic groups meta to the biphenyl link. X-ray crystal data of 15c complexed with TR-beta1 LBD shows methionine 442 to be displaced by the bulky R3' phenyl ethyl amide side chain. Movement of this amino acid side chain provides an expanded pocket for the bulky side chain while the ligand-receptor complex retains full agonist activity. 相似文献