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  • 1
    Publication Date: 2015-06-11
    Description: Gram-negative bacteria inhabit a broad range of ecological niches. For Escherichia coli, this includes river water as well as humans and animals, where it can be both a commensal and a pathogen. Intricate regulatory mechanisms ensure that bacteria have the right complement of beta-barrel outer membrane proteins (OMPs) to enable adaptation to a particular habitat. Yet no mechanism is known for replacing OMPs in the outer membrane, an issue that is further confounded by the lack of an energy source and the high stability and abundance of OMPs. Here we uncover the process underpinning OMP turnover in E. coli and show it to be passive and binary in nature, in which old OMPs are displaced to the poles of growing cells as new OMPs take their place. Using fluorescent colicins as OMP-specific probes, in combination with ensemble and single-molecule fluorescence microscopy in vivo and in vitro, as well as molecular dynamics simulations, we established the mechanism for binary OMP partitioning. OMPs clustered to form approximately 0.5-mum diameter islands, where their diffusion is restricted by promiscuous interactions with other OMPs. OMP islands were distributed throughout the cell and contained the Bam complex, which catalyses the insertion of OMPs in the outer membrane. However, OMP biogenesis occurred as a gradient that was highest at mid-cell but largely absent at cell poles. The cumulative effect is to push old OMP islands towards the poles of growing cells, leading to a binary distribution when cells divide. Hence, the outer membrane of a Gram-negative bacterium is a spatially and temporally organized structure, and this organization lies at the heart of how OMPs are turned over in the membrane.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rassam, Patrice -- Copeland, Nikki A -- Birkholz, Oliver -- Toth, Csaba -- Chavent, Matthieu -- Duncan, Anna L -- Cross, Stephen J -- Housden, Nicholas G -- Kaminska, Renata -- Seger, Urban -- Quinn, Diana M -- Garrod, Tamsin J -- Sansom, Mark S P -- Piehler, Jacob -- Baumann, Christoph G -- Kleanthous, Colin -- BB/G020671/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/L002558/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- WT092970MA/Wellcome Trust/United Kingdom -- England -- Nature. 2015 Jul 16;523(7560):333-6. doi: 10.1038/nature14461. Epub 2015 Jun 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK [2] Department of Biology, University of York, York YO10 5DD, UK. ; Department of Biology, University of York, York YO10 5DD, UK. ; Department of Biology, University of Osnabruck, Barbarastrasse 11, 49076 Osnabruck, Germany. ; Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26061769" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Outer Membrane Proteins/*chemistry/*metabolism ; Cell Polarity ; Diffusion ; Escherichia coli/chemistry/*cytology/genetics/*metabolism ; Escherichia coli Proteins/*chemistry/*metabolism ; Lipid-Linked Proteins/metabolism ; Microscopy, Confocal ; Microscopy, Fluorescence ; Molecular Dynamics Simulation ; Multiprotein Complexes/metabolism ; Protein Binding ; Protein Transport
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2015-03-15
    Description: TREK-2 (KCNK10/K2P10), a two-pore domain potassium (K2P) channel, is gated by multiple stimuli such as stretch, fatty acids, and pH and by several drugs. However, the mechanisms that control channel gating are unclear. Here we present crystal structures of the human TREK-2 channel (up to 3.4 angstrom resolution) in two conformations and in complex with norfluoxetine, the active metabolite of fluoxetine (Prozac) and a state-dependent blocker of TREK channels. Norfluoxetine binds within intramembrane fenestrations found in only one of these two conformations. Channel activation by arachidonic acid and mechanical stretch involves conversion between these states through movement of the pore-lining helices. These results provide an explanation for TREK channel mechanosensitivity, regulation by diverse stimuli, and possible off-target effects of the serotonin reuptake inhibitor Prozac.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dong, Yin Yao -- Pike, Ashley C W -- Mackenzie, Alexandra -- McClenaghan, Conor -- Aryal, Prafulla -- Dong, Liang -- Quigley, Andrew -- Grieben, Mariana -- Goubin, Solenne -- Mukhopadhyay, Shubhashish -- Ruda, Gian Filippo -- Clausen, Michael V -- Cao, Lishuang -- Brennan, Paul E -- Burgess-Brown, Nicola A -- Sansom, Mark S P -- Tucker, Stephen J -- Carpenter, Elisabeth P -- 084655/Wellcome Trust/United Kingdom -- 092809/Z/10/Z/Wellcome Trust/United Kingdom -- Biotechnology and Biological Sciences Research Council/United Kingdom -- New York, N.Y. -- Science. 2015 Mar 13;347(6227):1256-9. doi: 10.1126/science.1261512.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. ; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK. ; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. ; Pfizer Neusentis, Granta Park, Cambridge CB21 6GS, UK. ; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK. ; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. liz.carpenter@sgc.ox.ac.uk stephen.tucker@physics.ox.ac.uk. ; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. liz.carpenter@sgc.ox.ac.uk stephen.tucker@physics.ox.ac.uk.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25766236" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Arachidonic Acid/pharmacology ; Binding Sites ; Crystallography, X-Ray ; Fluoxetine/analogs & derivatives/chemistry/metabolism/pharmacology ; Humans ; *Ion Channel Gating ; Models, Molecular ; Molecular Dynamics Simulation ; Molecular Sequence Data ; Potassium/metabolism ; Potassium Channels, Tandem Pore Domain/antagonists & ; inhibitors/*chemistry/metabolism ; Protein Conformation ; Protein Folding ; Protein Structure, Secondary ; Protein Structure, Tertiary
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2015-04-28
    Description: : The volume of an internal protein pocket is fundamental to ligand accessibility. Few programs that compute such volumes manage dynamic data from molecular dynamics (MD) simulations. Limited performance often prohibits analysis of large datasets. We present Epock, an efficient command-line tool that calculates pocket volumes from MD trajectories. A plugin for the VMD program provides a graphical user interface to facilitate input creation, run Epock and analyse the results. Availability and implementation: Epock C++ source code, Python analysis scripts, VMD Tcl plugin, documentation and installation instructions are freely available at http://epock.bitbucket.org . Contact: benoist.laurent@gmail.com or baaden@smplinux.de Supplementary information: Supplementary data are available at Bioinformatics online.
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 4
    Publication Date: 2017-01-22
    Description: Pleckstrin homology (PH) domains are membrane-binding lipid recognition proteins that interact with phosphatidylinositol phosphate (PIP) molecules in eukaryotic cell membranes. Diffusion of PH domains plays a critical role in biological reactions on membrane surfaces. Although diffusivity can be estimated by long-time measurements, it lacks information on the short-time diffusive nature. We reveal two diffusive properties of a PH domain bound to the surface of a PIP-containing membrane using molecular dynamics simulations. One is fractional Brownian motion, attributed to the motion of the lipids with which the PH domain interacts. The other is temporally fluctuating diffusivity; that is, the short-time diffusivity of the bound protein changes substantially with time. Moreover, the diffusivity for short-time measurements is intrinsically different from that for long-time measurements. This fluctuating diffusivity results from dynamic changes in interactions between the PH domain and PIP molecules. Our results provide evidence that the complexity of protein-lipid interactions plays a crucial role in the diffusion of proteins on biological membrane surfaces. Changes in the diffusivity of PH domains and related membrane-bound proteins may in turn contribute to the formation/dissolution of protein complexes in membranes.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 5
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