| 1. |
- Jegerschöld, Caroline, et al.
(author)
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Structural basis for induced formation of the inflammatory mediator prostaglandin E-2
- 2008
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:32, s. 11110-11115
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Journal article (peer-reviewed)abstract
- Prostaglandins (PG) are bioactive lipids produced from arachidonic acid via the action of cyclooxygenases and terminal PG synthases. Microsomal prostaglandin E synthase 1 (MPGES1) constitutes an inducible glutathione-dependent integral membrane protein that catalyzes the oxidoreduction of cyclooxygenase derived PGH(2) into PGE(2). MPGES1 has been implicated in a number of human diseases or pathological conditions, such as rheumatoid arthritis, fever, and pain, and is therefore regarded as a primary target for development of novel antiinflammatory drugs. To provide a structural basis for insight in the catalytic mechanism, we determined the structure of MPGES1 in complex with glutathione by electron crystallography from 2D crystals induced in the presence of phospholipids. Together with results from site-directed mutagenesis and activity measurements, we can thereby demonstrate the role of specific amino acid residues. Glutathione is found to bind in a U-shaped conformation at the interface between subunits in the protein trimer. It is exposed to a site facing the lipid bilayer, which forms the specific environment for the oxidoreduction of PGH(2) to PGE(2) after displacement of the cytoplasmic half of the IN-terminal transmembrane helix. Hence, insight into the dynamic behavior of MPGES1 and homologous membrane proteins in inflammation and detoxification is provided.
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| 2. |
- Le Guillou, Y, et al.
(author)
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Highly integrated direct conversion receiver for GSM/GPRS/EDGE with on-chip 84-dB dynamic range continuous-time ΣΔ ADC
- 2005
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In: IEEE Journal of Solid-State Circuits. - 0018-9200. ; 40:2, s. 403-411
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Journal article (peer-reviewed)abstract
- This paper describes a highly digitized direct conversion receiver of a single-chip quadruple-band RF transceiver that meets GSM/GPRS and EDGE requirements. The chip uses an advanced 0.25-mum BiCMOS technology. The I and Q on-chip fifth-order single-bit continuous-time sigma-delta (SigmaDelta) ADC has 84-dB dynamic range over a total bandwidth of +/-135 kHz for an active area of 0.4 mm(2). Hence, most of the channel filtering is realized in a CMOS IC where digital processing-is achieved at a lower cost. The systematic analysis of dc offset at each stage of the design enables to perform the dc offset cancellation loop in the digital domain as well. The receiver operates at 2.7 V with a current consumption of 75 mA. A first-order substrate coupling analysis enables to optimize the floor plan strategy. As a result, the receiver has an area of 1.8 mm(2).
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| 3. |
- Pawelzik, Sven-Christian, et al.
(author)
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Identification of Key Residues Determining Species Differences in Inhibitor Binding of Microsomal Prostaglandin E Synthase-1
- 2010
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In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 285:38, s. 29254-29261
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Journal article (peer-reviewed)abstract
- Microsomal prostaglandin E synthase-1 (MPGES1) is induced during an inflammatory reaction from low basal levels by pro-inflammatory cytokines and subsequently involved in the production of the important mediator of inflammation, prostaglandin E-2. Nonsteroidal anti-inflammatory drugs prevent prostaglandin E-2 production by inhibiting the upstream enzymes cyclooxygenases 1 and 2. In contrast to these conventional drugs, a new generation of NSAIDs targets the terminal enzyme MPGES1. Some of these compounds potently inhibit human MPGES1 but do not have an effect on the rat orthologue. We investigated this interspecies difference in a rat/human chimeric form of the enzyme as well as in several mutants and identified key residues Thr-131, Leu-135, and Ala-138 in human MPGES1, which play a crucial role as gate keepers for the active site of MPGES1. These residues are situated in transmembrane helix 4, lining the entrance to the cleft between two subunits in the protein trimer, and regulate access of the inhibitor in the rat enzyme. Exchange toward the human residues in rat MPGES1 was accompanied with a gain of inhibitor activity, whereas exchange in human MPGES1 toward the residues found in rat abrogated inhibitor activity. Our data give evidence for the location of the active site at the interface between subunits in the homotrimeric enzyme and suggest a model of how the natural substratePGH(2), or competitive inhibitors of MPGES1, enter the active site via the phospholipid bilayer of the membrane.
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| 4. |
- Wernersson, Sven, et al.
(author)
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Rapid measurement of heteronuclear transverse relaxation rates using non-uniformly sampled R1ρ accordion experiments
- 2021
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In: Magnetic Resonance. - : Copernicus GmbH. - 2699-0016. ; 2:2, s. 571-587
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Journal article (peer-reviewed)abstract
- Multidimensional, heteronuclear NMR relaxation methods are used extensively to characterize the dynamics of biological macromolecules. Acquisition of relaxation datasets on proteins typically requires significant measurement time, often several days. Accordion spectroscopy offers a powerful means to shorten relaxation rate measurements by encoding the “relaxation dimension” into the indirect evolution period in multidimensional experiments. Time savings can also be achieved by non-uniform sampling (NUS) of multidimensional NMR data, which is used increasingly to improve spectral resolution or increase sensitivity per unit time. However, NUS is not commonly implemented in relaxation experiments, because most reconstruction algorithms are inherently nonlinear, leading to problems when estimating signal intensities, relaxation rate constants and their error bounds. We have previously shown how to avoid these shortcomings by combining accordion spectroscopy with NUS, followed by data reconstruction using sparse exponential mode analysis, thereby achieving a dramatic decrease in the total length of longitudinal relaxation experiments. Here, we present the corresponding transverse relaxation experiment, taking into account the special considerations required for its successful implementation in the framework of the accordion-NUS approach. We attain the highest possible precision in the relaxation rate constants by optimizing the NUS scheme with respect to the Cramér-Rao lower bound of the variance of the estimated parameter, given the total number of sampling points and the spectrum-specific signal characteristics. The resulting accordion-NUS R1ρ relaxation experiment achieves comparable precision in the parameter estimates compared to conventional CPMG (Carr-Purcell-Meiboom-Gill) R2 or spin-lock R1ρ experiments while saving an order of magnitude in experiment time.
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