656 research outputs found

    A P-type ATPase importer that discriminates between essential and toxic transition metals

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    Transition metals, although being essential cofactors in many physiological processes, are toxic at elevated concentrations. Among the membrane-embedded transport proteins that maintain appropriate intracellular levels of transition metals are ATP-driven pumps belonging to the P-type ATPase superfamily. These metal transporters may be differentiated according to their substrate specificities, where the majority of pumps can extrude either silver and copper or zinc, cadmium, and lead. In the present report, we have established the substrate specificities of nine previously uncharacterized prokaryotic transition-metal P-type ATPases. We find that all of the newly identified exporters indeed fall into one of the two above-mentioned categories. In addition to these exporters, one importer, Pseudomonas aeruginosa Q9I147, was also identified. This protein, designated HmtA (heavy metal transporter A), exhibited a different substrate recognition profile from the exporters. In vivo metal susceptibility assays, intracellular metal measurements, and transport experiments all suggest that HmtA mediates the uptake of copper and zinc but not of silver, mercury, or cadmium. The substrate selectivity of this importer ensures the high-affinity uptake of essential metals, while avoiding intracellular contamination by their toxic counterparts

    Could recombinant insulin compounds contribute to adenocarcinoma progression by stimulating local angiogenesis?

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    Negative effects on the progression of adenocarcinomas by hyperinsulinaemia and the insulin analogue glargine (A21Gly,B31Arg,B32Arg human insulin) have recently been suggested. Most actions of this insulin analogue have hitherto been explained by direct stimulation of growth potential of neoplastic cells and by its IGF-1 related properties. However, insulin-stimulated angiogenesis could be an additional factor involved in tumour progression and clinical outcomes associated with cancer. Five types of human adenocarcinoma (breast, colon, pancreas, lung and kidney) were evaluated for the presence of insulin receptors (IRs) on angiogenic structures. In an in vitro angiogenesis assay, various commercially available insulin compounds were evaluated for their potential to increase capillary-like tube formation of human microvascular endothelial cells (hMVEC). Insulin compounds used were: human insulin, insulin lispro (B28Lys,B29Pro human insulin), insulin glargine and insulin detemir (B29Lys[e-tetradecanoyl],desB30 human insulin). Insulin receptors were found to be strongly expressed on the endothelium of microvessels in all evaluated adenocarcinomas, in addition to variable expression on tumour cells. Low or no detectable expression of IRs was seen on microvessels in extratumoral stroma. Incubation with commercially available insulin compounds increased capillary-like tube formation of hMVEC in vitro. Our results suggest that all tested insulin compounds may stimulate tumour growth by enhancing local angiogenesis. Future studies need to confirm the association between insulin therapy in type 2 diabetes and tumour progressio

    Bacterial resistance to arsenic protects against protist killing

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    Protists kill their bacterial prey using toxic metals such as copper. Here we hypothesize that the metalloid arsenic has a similar role. To test this hypothesis, we examined intracellular survival of Escherichia coli (E. coli) in the amoeba Dictyostelium discoideum (D. discoideum). Deletion of the E. coli ars operon led to significantly lower intracellular survival compared to wild type E. coli. This suggests that protists use arsenic to poison bacterial cells in the phagosome, similar to their use of copper. In response to copper and arsenic poisoning by protists, there is selection for acquisition of arsenic and copper resistance genes in the bacterial prey to avoid killing. In agreement with this hypothesis, both copper and arsenic resistance determinants are widespread in many bacterial taxa and environments, and they are often found together on plasmids. A role for heavy metals and arsenic in the ancient predator–prey relationship between protists and bacteria could explain the widespread presence of metal resistance determinants in pristine environments

    Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays

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    Average charged multiplicities have been measured separately in bb, cc and light quark (u,d,su,d,s) events from Z0Z^0 decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of bb and light quark events, and reconstructed charmed mesons were used to select cc quark events. We measured the charged multiplicities: nˉuds=20.21±0.10(stat.)±0.22(syst.)\bar{n}_{uds} = 20.21 \pm 0.10 (\rm{stat.})\pm 0.22(\rm{syst.}), nˉc=21.28±0.46(stat.)0.36+0.41(syst.)\bar{n}_{c} = 21.28 \pm 0.46(\rm{stat.}) ^{+0.41}_{-0.36}(\rm{syst.}) nˉb=23.14±0.10(stat.)0.37+0.38(syst.)\bar{n}_{b} = 23.14 \pm 0.10(\rm{stat.}) ^{+0.38}_{-0.37}(\rm{syst.}), from which we derived the differences between the total average charged multiplicities of cc or bb quark events and light quark events: Δnˉc=1.07±0.47(stat.)0.30+0.36(syst.)\Delta \bar{n}_c = 1.07 \pm 0.47(\rm{stat.})^{+0.36}_{-0.30}(\rm{syst.}) and Δnˉb=2.93±0.14(stat.)0.29+0.30(syst.)\Delta \bar{n}_b = 2.93 \pm 0.14(\rm{stat.})^{+0.30}_{-0.29}(\rm{syst.}). We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters

    Импортозамещение межсекционных уплотнений на примере многоступенчатого насоса "Grundfos"

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    Bronchoconstriction is a characteristic symptom of various chronic obstructive respiratory diseases such as chronic obstructive pulmonary disease (COPD) and asthma. Precision-cut lung slices (PCLS) are a suitable ex vivo model to study physiological mechanisms of bronchoconstriction in different species. In the present study, we established an ex vivo model of bronchoconstriction in non-human primates (NHPs). PCLS prepared from common marmosets, cynomolgus macaques, rhesus macaques, and anubis baboons were stimulated with increasing concentrations of representative bronchoconstrictors: methacholine, histamine, serotonin, leukotriene D4 (LTD4), U46619, and endothelin-1. Alterations in the airway caliber were measured and compared to previously published data from rodents, guinea pigs, and humans. Methacholine induced maximal airway constriction, varying between 74 and 88% in all NHP species, whereas serotonin was ineffective. Histamine induced maximal bronchoconstriction of 77 to 90% in rhesus macaques, cynomolgus macaques, and baboons, and a lesser constriction of 53% in marmosets. LTD4 was ineffective in marmosets and rhesus macaques, but induced a maximum constriction of 44 to 49% in cynomolgus macaques and baboons. U46619 and endothelin-1 caused airway constriction in all NHP species, with maximum constrictions of 65 to 91%, and 70 to 81%, respectively. In conclusion, PCLS from NHPs represent a valuable ex vivo model for studying bronchoconstriction. All NHPs respond to mediators relevant to human airway disorders such as methacholine, histamine, U46619, endothelin-1 and are insensitive to the rodent mast cell product serotonin. Only PCLS from cynomolgus macaques and baboons, however, responded also to leukotrienes, suggesting that among all compared species, these two NHPs resemble the human airway mechanisms bes

    In-cell NMR in E. coli to Monitor Maturation Steps of hSOD1

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    In-cell NMR allows characterizing the folding state of a protein as well as posttranslational events at molecular level, in the cellular context. Here, the initial maturation steps of human copper, zinc superoxide dismutase 1 are characterized in the E. coli cytoplasm by in-cell NMR: from the apo protein, which is partially unfolded, to the zinc binding which causes its final quaternary structure. The protein selectively binds only one zinc ion, whereas in vitro also the copper site binds a non-physiological zinc ion. However, no intramolecular disulfide bridge formation occurs, nor copper uptake, suggesting the need of a specific chaperone for those purposes