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Department of NanoBiophotonics
1,278
Total Impact Points
28
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Department of NMR-based Structural Biology
644
Total Impact Points
26
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Department of Theoretical and Computational Biophysics
372
Total Impact Points
19
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Publication History View all

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    ABSTRACT: The DNA packaging motor of the bacteriophage ϕ29, comprising head-tail connector, ATPase, and pRNA, transports the viral DNA inside the procapsid against pressure differences of up to ∼60 atm during replication. Several models for the DNA packaging mechanism have been proposed, which attribute different roles to the connector, and require specific mechanical properties of the connector. To characterize these properties at the atomic level, and to understand how the connector withstands this large pressure, we have carried out molecular dynamics simulations of the whole connector both in equilibrium and under mechanical stress. The simulations revealed a quite heterogeneous distribution of stiff and soft regions, resembling that of typical composite materials that are also optimized to resist mechanical stress. In particular, the conserved middle α-helical region is found to be remarkably stiff, similar only to structural proteins forming viral shell, silk, or collagen. In contrast, large parts of the peripheral interface to the ϕ29 procapsid turned out to be rather soft. Force probe and umbrella sampling simulations showed that large connector deformations are remarkably reversible, and served to calculate the free energies required for these deformations. In particular, for an untwisting deformation by 12°, as postulated by the untwist-twist model, more than four times’ larger energy is required than is available from hydrolysis of one ATP molecule. Combined with previous experiments, this result is incompatible with the untwist-twist model. In contrast, our simulations support the recently proposed one-way revolution model and suggest in structural terms how the connector blocks DNA leakage. In particular, conserved loops at the rim of the central channel, which are in direct contact with the DNA, are found to be rather flexible and tightly anchored to the rigid central region. These findings suggest a check-valve mechanism, with the flexible loops obstructing the channel by interacting with the viral DNA.
    Biophysical Journal 03/2014; 106(6):1338-1348.
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    ABSTRACT: Adaptive mobilization of body fat is essential for energy homeostasis in animals. In insects, the adipokinetic hormone (AKH) systemically controls body fat mobilization. Biochemical evidence supports that AKH signals via a G protein-coupled receptor (GPCR) called AKH receptor (AKHR) using cyclic-AMP (cAMP) and Ca2+ second messengers to induce storage lipid release from fat body cells. Recently, we provided genetic evidence that the intracellular calcium (iCa2+) level in fat storage cells controls adiposity in the fruit fly Drosophila melanogaster. However, little is known about the genes, which mediate AKH signalling downstream of the AKHR to regulate changes in iCa2+. Here, we used thermogenetics to provide in vivo evidence that the GPCR signal transducers G protein α q subunit (Gαq), G protein γ1 (Gγ1) and Phospholipase C at 21C (Plc21C) control cellular and organismal fat storage in Drosophila. Transgenic modulation of Gαq, Gγ1 and Plc21C affected the iCa2+ of fat body cells and the expression profile of the lipid metabolism effector genes midway and brummer, which results in severely obese or lean flies. Moreover, functional impairment of Gαq, Gγ1 and Plc21C antagonised AKH-induced fat depletion. This study characterized Gαq, Gγ1 and Plc21C as anti-obesity genes and supported the model that AKH employs the Gαq/Gγ1/Plc21C module of iCa2+ control to regulate lipid mobilization in adult Drosophila.
    Journal of Genetics and Genomics 01/2014;
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    ABSTRACT: The regulatory role of histone modifications with respect to the structure and function of chromatin is well known. Proteins and protein complexes establishing, erasing and binding these marks have been extensively studied. RNAs have only recently entered the picture of epigenetic regulation with the discovery of a vast number of long non-coding RNAs. Fast growing evidence suggests that such RNAs influence all aspects of histone modification biology. Here, we focus exclusively on the emerging functional interplay between RNAs and proteins that bind histone modifications. We discuss recent findings of reciprocally positive and negative regulation as well as summarize the current insights into the molecular mechanism directing these interactions. This article is part of a Special Issue entitled: Molecular mechanisms of histone modification function, edited by Dr. Wolfgang Fischle.
    Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms 01/2014;

Information

  • Address
    Am Faßberg 11, 37077, Göttingen, Lower Saxony, Germany
  • Head of Institution
    Gregor Eichele
  • Website
    http://www.mpibpc.mpg.de/en
  • Phone
    551-201-2705
  • Fax
    551-201-2700
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Methods in molecular biology (Clifton, N.J.) 02/2007; 374:69-79.
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