In July 2012, as the four ground-based gamma-ray telescopes of the H.E.S.S. (High Energy Stereoscopic System) array reached their tenth year of operation in Khomas Highlands, Namibia, a fifth ...telescope took its first data as part of the system. This new Cherenkov detector, comprising a 614.5m2 reflector with a highly pixelized camera in its focal plane, improves the sensitivity of the current array by a factor two and extends its energy domain down to a few tens of GeV.
The present part I of the paper gives a detailed description of the fifth H.E.S.S. telescope׳s camera, presenting the details of both the hardware and the software, emphasizing the main improvements as compared to previous H.E.S.S. camera technology.
Size determination represents a fundamental requirement for multicomponent biological structures. Some pathogenic bacteria possess a weapon derived from the flagellum. Like the flagellum, this ...type-III secretion apparatus, called the injectisome, has a transmembrane basal body, but the external component is a needle-like structure instead of a hook and a filament. Here, we provide evidence that the length of this needle is determined by the size of a protein, YscP, acting as a molecular ruler.
Bacterial Injectisomes: Needle Length Does Matter Mota, Luís Jaime; Journet, Laure; Sorg, Isabel ...
Science (American Association for the Advancement of Science),
02/2005, Letnik:
307, Številka:
5713
Journal Article
Recenzirano
Many pathogenic bacteria use a type III secretion nanomachine (an injectisome) to deliver virulence proteins into the cytosol of their eukaryotic host cells. Most injectisomes possess a stiff ...needlelike structure of a genetically defined length. We found that a minimal needle length was required for efficient functioning of the Yersinia enterocolitica injectisome. This minimal needle length correlated with the length of the major adhesin at the bacterial surface. The needle may be required for triggering type III secretion, and its length may have evolved to match specific structures at the bacterial and host cell surfaces.
The AMS-02 lead-scintillating fibres Electromagnetic Calorimeter Adloff, C.; Basara, L.; Bigongiari, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2013, Letnik:
714
Journal Article
Recenzirano
The Electromagnetic Calorimeter (ECAL) of the AMS-02 experiment is a fine grained lead-scintillating fibres sampling calorimeter that allows for a precise three-dimensional imaging of the ...longitudinal and lateral shower development. It provides a high (≥106) electron/hadron discrimination with the other AMS-02 detectors 1 and good energy resolution. The calorimeter also provides a standalone photon trigger capability to AMS-02. The mechanical assembly was realized to ensure minimum weight, still supporting the intrinsically heavy calorimeter during launch. ECAL light collection system and electronics are designed to measure electromagnetic particles over a wide energy range, from GeV up to TeV. A full-scale flight-like model was tested using electrons and proton beams with energies ranging from 6 to 250GeV.
Summary
The length of the needle ending the Yersinia Ysc injectisome is determined by YscP, a protein acting as a molecular ruler. In addition, YscP is required for Yop secretion. In the present ...paper, by a systematic deletion analysis, we localized accurately the region required for Yop secretion between residues 405 and 500. As this C‐terminal region of YscP has also been shown to control needle length it probably represents the substrate specificity switch of the machinery. By a bioinformatics analysis, we show that this region has a globular structure, an original α/β fold, a P‐x‐L‐G signature and presumably no catalytic activity. In spite of very limited sequence similarities, this structure is conserved among the proteins that are presumed to control the needle length in many different injectisomes and also among members of the FliK family, which control the flagellar hook length. This region thus represents a new protein domain that we called T3S4 for Type III secretion substrate specificity switch. The T3S4 domain of YscP can be replaced by the T3S4 domain of AscP (Aeromonas salmonicida) or PscP (Pseudomonas aeruginosa) but not by the one from FliK, indicating that in spite of a common global structure, these domains need to fit their partner proteins in the secretion apparatus.
The outer membrane of Gram-negative bacteria acts as a barrier against harmful lipophilic compounds and larger molecules unable to diffuse freely through the porins. However, outer membrane proteins ...together with the Tol-Pal and TonB systems have been exploited for the entry of macromolecules such as bacteriocins and phage DNA through the
Escherichia coli cell envelope. The TonB system is involved in the active transport of iron siderophores and vitamin B12, while no more precise physiological role of the Tol-Pal system has yet been defined than its requirement for cell envelope integrity. These two systems, containing an energized inner membrane protein interacting with outer membrane proteins, share similarities.
'Type III secretion' (T3S) refers to a secretion pathway that is common to the flagellae of eubacteria and the injectisomes of some Gram-negative bacteria. Flagellae are rotary nanomachines allowing ...motility but they contain a built-in secretion apparatus that exports their own distal components to the distal end of the growing structure where they polymerize. In some cases they have been shown to export non-flagellar proteins. Injectisomes are transkingdom communication apparatuses allowing bacteria docked at the surface of a eukaryotic cell membrane to inject effector proteins across the two bacterial membranes and the eukaryotic cell membrane. Both nanomachines share a similar basal body embedded in the two bacterial membranes, topped either by a hook and a filament or by a stiff short needle. Both appear to be assembled in the same fashion. They recognize their substrate by a loose N-terminal peptide signal and the help of individual chaperones of a new type.
Outer membrane vesicle formation occurs during Gram-negative bacterial growth. However, natural production of large amounts of outer membrane vesicles has only been described in a few bacterial ...genera. The purified vesicles of some bacterial pathogens have shown potential applications in vaccinology and in antibiotic therapy. This study focused on the development of a gene expression system able to induce production of large amounts of outer membrane vesicles. The Tol–Pal system of
Escherichia coli, required to maintain outer membrane integrity, is composed of five cell envelope proteins, TolA, TolB, TolQ, TolR and Pal. Tol proteins are parasitized by filamentous bacteriophages and by colicins. The phage infection process and colicin import require, respectively, the N-terminal domain of the minor coat g3p protein and the translocation domain of colicins, with both domains interacting with Tol proteins. In this study, we show that the periplasmic production of either Tol, g3p or colicin domains was able to specifically destabilize the
E. coli or
Shigella flexneri cell envelope and to induce production of high amounts of vesicles. This technique was further found to work efficiently in
Salmonella enterica serovar Typhimurium.
FpvA is an outer membrane transporter involved in iron uptake by the siderophore pyoverdine (Pvd) in Pseudomonas aeruginosa. This transporter, like all other proteins of the same family, consists of ...a transmembrane 22 β-stranded barrel occluded by a plug domain. The β-strands of the barrel are connected by large extracellular loops and short periplasmic turns. Site-directed mutagenesis was carried out on FpvA to identify the extracellular loops or parts of these loops involved in the various stages of Pvd−Fe uptake. The G286C, W362C, and W434C mutations in loops L1, L3, and L4, respectively, disturbed the binding of the apo siderophore, as shown by time-resolved fluorescence spectroscopy. Iron uptake experiments followed by fluorescence resonance energy transfer (FRET) or using 55Fe indicated that residues W434 and G701 and, therefore, loops L4 and L9 must be involved in Pvd−Fe uptake by FpvA. The two corresponding mutants incorporated smaller than normal amounts of 55Fe into cells, and no Pvd recycling on FpvA was observed after iron release. Surprisingly, the S603C mutation in loop L7 increased the amount of Pvd−Fe transported. Our results suggest that W434 (L4), S603 (L7), and G701 (L9) are involved in the mechanism of Pvd−Fe uptake.
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