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991.
Bruno Alies Vincent Pradines Isabelle Llorens-Alliot Stéphanie Sayen Emmanuel Guillon Christelle Hureau Peter Faller 《Journal of biological inorganic chemistry》2011,16(2):333-340
Metal ions such as zinc and copper can have dramatic effects on the aggregation kinetics of and the structures formed by several
amyloidogenic peptides/proteins. Depending on the identity of the amyloidogenic peptide/protein and the conditions, Zn(II)
and Cu(II) can promote or inhibit fibril formation, and in some cases these metal ions have opposite effects. To better understand
this modulation of peptide aggregation by metal ions, the impact of Zn(II) binding to three amyloidogenic peptides (Aβ14-23,
Aβ11-23, and Aβ11-28) on the formation and structure of amyloid-type fibrils was investigated. Zn(II) was able to accelerate
fibril formation for all three peptides as measured by thioflavin T fluorescence and transmission electron microscopy. The
effects of Zn(II) on Aβ11-23 and Aβ11-28 aggregation were very different compared with the effects of Cu(II), showing that
these promoting effects were metal-specific. X-ray absorption spectroscopy suggested that the Zn(II) binding to Aβ11-23 and
Aβ11-28 is very different from Cu(II) binding, but that the binding is similar in the case of Aβ14-23. A model is proposed
in which the different coordination chemistry of Zn(II) compared with Cu(II) explains the metal-specific effect on aggregation
and the difference between peptides Aβ14-23 and Aβ11-23/Aβ11-28. 相似文献
992.
Sialyltransferases (STs) represent an important group of enzymes that transfer N-acetylneuraminic acid (Neu5Ac) from cytidine monophosphate-Neu5Ac to various acceptor substrates. In higher animals, sialylated oligosaccharide structures play crucial roles in many biological processes but also in diseases, notably in microbial infection and cancer. Cell surface sialic acids have also been found in a few microorganisms, mainly pathogenic bacteria, and their presence is often associated with virulence. STs are distributed into five different families in the CAZy database (http://www.cazy.org/). On the basis of crystallographic data available for three ST families and fold recognition analysis for the two other families, STs can be grouped into two structural superfamilies that represent variations of the canonical glycosyltransferase (GT-A and GT-B) folds. These two superfamilies differ in the nature of their active site residues, notably the catalytic base (a histidine or an aspartate residue). The observed structural and functional differences strongly suggest that these two structural superfamilies have evolved independently. 相似文献
993.
994.
Marcet B Chevalier B Luxardi G Coraux C Zaragosi LE Cibois M Robbe-Sermesant K Jolly T Cardinaud B Moreilhon C Giovannini-Chami L Nawrocki-Raby B Birembaut P Waldmann R Kodjabachian L Barbry P 《Nature cell biology》2011,13(6):693-699
Multiciliated cells lining the surface of some vertebrate epithelia are essential for various physiological processes, such as airway cleansing. However, the mechanisms governing motile cilia biosynthesis remain poorly elucidated. We identify miR-449 microRNAs as evolutionarily conserved key regulators of vertebrate multiciliogenesis. In human airway epithelium and Xenopus laevis embryonic epidermis, miR-449 microRNAs strongly accumulated in multiciliated cells. In both models, we show that miR-449 microRNAs promote centriole multiplication and multiciliogenesis by directly repressing the Delta/Notch pathway. We established Notch1 and its ligand Delta-like 1(DLL1) as miR-449 bona fide targets. Human DLL1 and NOTCH1 protein levels were lower in multiciliated cells than in surrounding cells, decreased after miR-449 overexpression and increased after miR-449 inhibition. In frog, miR-449 silencing led to increased Dll1 expression. Consistently, overexpression of Dll1 mRNA lacking miR-449 target sites repressed multiciliogenesis, whereas both Dll1 and Notch1 knockdown rescued multiciliogenesis in miR-449-deficient cells. Antisense-mediated protection of miR-449-binding sites of endogenous human Notch1 or frog Dll1 strongly repressed multiciliogenesis. Our results unravel a conserved mechanism whereby Notch signalling must undergo miR-449-mediated inhibition to permit differentiation of ciliated cell progenitors. 相似文献
995.
996.
Andrew Dauber Christelle Golzio Cécile Guenot Francine?M. Jodelka Maria Kibaek Susanne Kjaergaard Bruno Leheup Danielle Martinet Malgorzata?J.M. Nowaczyk Jill?A. Rosenfeld Susan Zeesman Janice Zunich Jacques?S. Beckmann Joel?N. Hirschhorn Michelle?L. Hastings Sebastien Jacquemont Nicholas Katsanis 《American journal of human genetics》2013,93(5):994-811
997.
Andrew Dauber Christelle Golzio Cécile Guenot Francine M. Jodelka Maria Kibaek Susanne Kjaergaard Bruno Leheup Danielle Martinet Malgorzata J.M. Nowaczyk Jill A. Rosenfeld Susan Zeesman Janice Zunich Jacques S. Beckmann Joel N. Hirschhorn Michelle L. Hastings Sebastien Jacquemont Nicholas Katsanis 《American journal of human genetics》2013
998.
Boniface M. Mailu Gowthaman Ramasamay Devaraja G. Mudeppa Ling Li Scott E. Lindner Megan J. Peterson Amy E. DeRocher Stefan H. I. Kappe Pradipsinh K. Rathod Malcolm J. Gardner 《The Journal of biological chemistry》2013,288(45):32539-32552
The malaria parasite Plasmodium falciparum and related organisms possess a relict plastid known as the apicoplast. Apicoplast protein synthesis is a validated drug target in malaria because antibiotics that inhibit translation in prokaryotes also inhibit apicoplast protein synthesis and are sometimes used for malaria prophylaxis or treatment. We identified components of an indirect aminoacylation pathway for Gln-tRNAGln biosynthesis in Plasmodium that we hypothesized would be essential for apicoplast protein synthesis. Here, we report our characterization of the first enzyme in this pathway, the apicoplast glutamyl-tRNA synthetase (GluRS). We expressed the recombinant P. falciparum enzyme in Escherichia coli, showed that it is nondiscriminating because it glutamylates both apicoplast tRNAGlu and tRNAGln, determined its kinetic parameters, and demonstrated its inhibition by a known bacterial GluRS inhibitor. We also localized the Plasmodium berghei ortholog to the apicoplast in blood stage parasites but could not delete the PbGluRS gene. These data show that Gln-tRNAGln biosynthesis in the Plasmodium apicoplast proceeds via an essential indirect aminoacylation pathway that is reminiscent of bacteria and plastids. 相似文献
999.
Christelle Tougard Sophie Montuire Vitaly Volobouev Evgenia Markova Julien Contet Vladimir Aniskin Jean‐Pierre Quere 《Biological journal of the Linnean Society. Linnean Society of London》2013,108(2):434-452
Natural hybridization between species is not a rare event. In arvicoline rodents, hybridization is known to occur in the wild and/or in captivity. In the Microtus arvalis group, cytogenetic studies revealed that there were two distinct chromosomal forms (2n = 46 but a different fundamental number of autosomes). These forms have been attributed to two cryptic species: the common (arvalis) and Altai (obscurus) voles. Recently, individuals with intermediate karyotypes (F1 and backcrosses) were discovered in central European Russia, and, for this reason, other studies have regarded obscurus and arvalis as conspecific. In the present study, to address the question of the species limits in the Altai vole and to infer its evolutionary history, a phylogeographical analysis combined with multivariate morphometric methods and original chromosome data was performed. Two obscurus lineages were identified: the Sino‐Russian and South Caucasian lineages. Both lineages are characterized by low genetic diversity, resulting, in the former, from a past bottleneck event caused by encroaching periglacial areas and, in the latter, from recent rapid population divergence. Introgressive hybridization between the Altai and common voles appears to be the result of a secondary contact following the Last Glacial Maximum in central European Russia. Despite the fact that speciation is an ongoing process in most arvicoline species, the common and Altai voles are genetically divergent, morphologically and karyologically distinct, and exhibit contrasting evolutionary histories. For all these reasons, they should be ranked as species: M. arvalis and M. obscurus. © 2013 The Linnean Society of London 相似文献