| 1. |
- Dago, Angel E, et al.
(författare)
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Structural basis of histidine kinase autophosphorylation deduced by integrating genomics, molecular dynamics, and mutagenesis
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:26, s. E1733-E1742
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Tidskriftsartikel (refereegranskat)abstract
- Signal transduction proteins such as bacterial sensor histidine kinases, designed to transition between multiple conformations, are often ruled by unstable transient interactions making structural characterization of all functional states difficult. This study explored the inactive and signal-activated conformational states of the two catalytic domains of sensor histidine kinases, HisKA and HATPase. Direct coupling analyses, a global statistical inference approach, was applied to >13,000 such domains from protein databases to identify residue contacts between the two domains. These contacts guided structural assembly of the domains using MAGMA, an advanced molecular dynamics docking method. The active conformation structure generated by MAGMA simultaneously accommodated the sequence derived residue contacts and the ATP-catalytic histidine contact. The validity of this structure was confirmed biologically by mutation of contact positions in the Bacillus subtilis sensor histidine kinase KinA and by restoration of activity in an inactive KinA(HisKA):KinD(HATPase) hybrid protein. These data indicate that signals binding to sensor domains activate sensor histidine kinases by causing localized strain and unwinding at the end of the C-terminal helix of the HisKA domain. This destabilizes the contact positions of the inactive conformation of the two domains, identified by previous crystal structure analyses and by the sequence analysis described here, inducing the formation of the active conformation. This study reveals that structures of unstable transient complexes of interacting proteins and of protein domains are accessible by applying this combination of cross-validating technologies.
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| 2. |
- Hederstedt, Lars, et al.
(författare)
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Krebs´ citric acid cycle
- 1993
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Ingår i: <em>Bacillus</em> and other gram-positive bacteria. - Washington, DC, USA : ASM Press. - 9781555818388 ; , s. 181-197
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Bokkapitel (refereegranskat)abstract
- The citric acid cycle (CAC) has several functions in aerobic bacteria. Together with the pyruvate dehydrogenase multienzyme complex (PDHC), it completely oxidizes pyruvate and provides membrane-bound respiratory systems with reducing equivalents. An overview of the biochemistry and genetics of CAC enzymes in B. subtilis is presented in this chapter. B. subtilis, being a strict aerobe, runs a complete CAC, as is demonstrated by enzyme activity measurements with cell extracts or purified enzymes and by the ability of this bacterium to grow on most of the intermediates of the CAC as sole carbon source. 2-oxoglutarate dehydrogenase multienzyme complex (ODHC) belongs to the same family of enzymes as PDHC. Present knowledge of this enzyme, has been acquired from studies involving various B. subtilis mutants. The prosthetic groups of B. subtilis SQR and some of their properties are presented in this chapter. The occurrence of larger and smaller types of malate dehydrogenase seems not to be correlated with gram-positive or gram-negative bacteria as citrate synthase and succinate thiokinase are. Little information on the genetics of malate dehydrogenase in gram-positive bacteria is available, but B. subtilis mutants defective in this CAC enzyme have been isolated.
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| 3. |
- Hinkley, Sasha, et al.
(författare)
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The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems
- 2022
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1039
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Tidskriftsartikel (refereegranskat)abstract
- The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ∼15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles.
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