排序方式: 共有91条查询结果,搜索用时 15 毫秒
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Yip CK Kimbrough TG Felise HB Vuckovic M Thomas NA Pfuetzner RA Frey EA Finlay BB Miller SI Strynadka NC 《Nature》2005,435(7042):702-707
Type III secretion systems (TTSSs) are multi-protein macromolecular 'machines' that have a central function in the virulence of many Gram-negative pathogens by directly mediating the secretion and translocation of bacterial proteins (termed effectors) into the cytoplasm of eukaryotic cells. Most of the 20 unique structural components constituting this secretion apparatus are highly conserved among animal and plant pathogens and are also evolutionarily related to proteins in the flagellar-specific export system. Recent electron microscopy experiments have revealed the gross 'needle-shaped' morphology of the TTSS, yet a detailed understanding of the structural characteristics and organization of these protein components within the bacterial membranes is lacking. Here we report the 1.8-A crystal structure of EscJ from enteropathogenic Escherichia coli (EPEC), a member of the YscJ/PrgK family whose oligomerization represents one of the earliest events in TTSS assembly. Crystal packing analysis and molecular modelling indicate that EscJ could form a large 24-subunit 'ring' superstructure with extensive grooves, ridges and electrostatic features. Electron microscopy, labelling and mass spectrometry studies on the orthologous Salmonella typhimurium PrgK within the context of the assembled TTSS support the stoichiometry, membrane association and surface accessibility of the modelled ring. We propose that the YscJ/PrgK protein family functions as an essential molecular platform for TTSS assembly. 相似文献
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Kulaga HM Leitch CC Eichers ER Badano JL Lesemann A Hoskins BE Lupski JR Beales PL Reed RR Katsanis N 《Nature genetics》2004,36(9):994-998
Defects in cilia are associated with several human disorders, including Kartagener syndrome, polycystic kidney disease, nephronophthisis and hydrocephalus. We proposed that the pleiotropic phenotype of Bardet-Biedl syndrome (BBS), which encompasses retinal degeneration, truncal obesity, renal and limb malformations and developmental delay, is due to dysfunction of basal bodies and cilia. Here we show that individuals with BBS have partial or complete anosmia. To test whether this phenotype is caused by ciliary defects of olfactory sensory neurons, we examined mice with deletions of Bbs1 or Bbs4. Loss of function of either BBS protein affected the olfactory, but not the respiratory, epithelium, causing severe reduction of the ciliated border, disorganization of the dendritic microtubule network and trapping of olfactory ciliary proteins in dendrites and cell bodies. Our data indicate that BBS proteins have a role in the microtubule organization of mammalian ciliated cells and that anosmia might be a useful determinant of other pleiotropic disorders with a suspected ciliary involvement. 相似文献
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It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. 相似文献
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Mutations in the chromatin modifier gene KANSL1 cause the 17q21.31 microdeletion syndrome 总被引:1,自引:0,他引:1
Koolen DA Kramer JM Neveling K Nillesen WM Moore-Barton HL Elmslie FV Toutain A Amiel J Malan V Tsai AC Cheung SW Gilissen C Verwiel ET Martens S Feuth T Bongers EM de Vries P Scheffer H Vissers LE de Brouwer AP Brunner HG Veltman JA Schenck A Yntema HG de Vries BB 《Nature genetics》2012,44(6):639-641
We show that haploinsufficiency of KANSL1 is sufficient to cause the 17q21.31 microdeletion syndrome, a multisystem disorder characterized by intellectual disability, hypotonia and distinctive facial features. The KANSL1 protein is an evolutionarily conserved regulator of the chromatin modifier KAT8, which influences gene expression through histone H4 lysine 16 (H4K16) acetylation. RNA sequencing studies in cell lines derived from affected individuals and the presence of learning deficits in Drosophila melanogaster mutants suggest a role for KANSL1 in neuronal processes. 相似文献
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Graubert TA Shen D Ding L Okeyo-Owuor T Lunn CL Shao J Krysiak K Harris CC Koboldt DC Larson DE McLellan MD Dooling DJ Abbott RM Fulton RS Schmidt H Kalicki-Veizer J O'Laughlin M Grillot M Baty J Heath S Frater JL Nasim T Link DC Tomasson MH Westervelt P DiPersio JF Mardis ER Ley TJ Wilson RK Walter MJ 《Nature genetics》2012,44(1):53-57
Myelodysplastic syndromes (MDS) are hematopoietic stem cell disorders that often progress to chemotherapy-resistant secondary acute myeloid leukemia (sAML). We used whole-genome sequencing to perform an unbiased comprehensive screen to discover the somatic mutations in a sample from an individual with sAML and genotyped the loci containing these mutations in the matched MDS sample. Here we show that a missense mutation affecting the serine at codon 34 (Ser34) in U2AF1 was recurrently present in 13 out of 150 (8.7%) subjects with de novo MDS, and we found suggestive evidence of an increased risk of progression to sAML associated with this mutation. U2AF1 is a U2 auxiliary factor protein that recognizes the AG splice acceptor dinucleotide at the 3' end of introns, and the alterations in U2AF1 are located in highly conserved zinc fingers of this protein. Mutant U2AF1 promotes enhanced splicing and exon skipping in reporter assays in vitro. This previously unidentified, recurrent mutation in U2AF1 implicates altered pre-mRNA splicing as a potential mechanism for MDS pathogenesis. 相似文献
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Wnk4 controls blood pressure and potassium homeostasis via regulation of mass and activity of the distal convoluted tubule 总被引:10,自引:0,他引:10
Lalioti MD Zhang J Volkman HM Kahle KT Hoffmann KE Toka HR Nelson-Williams C Ellison DH Flavell R Booth CJ Lu Y Geller DS Lifton RP 《Nature genetics》2006,38(10):1124-1132
The mechanisms that govern homeostasis of complex systems have been elusive but can be illuminated by mutations that disrupt system behavior. Mutations in the gene encoding the kinase WNK4 cause pseudohypoaldosteronism type II (PHAII), a syndrome featuring hypertension and hyperkalemia. We show that physiology in mice transgenic for genomic segments harboring wild-type (TgWnk4(WT)) or PHAII mutant (TgWnk4(PHAII)) Wnk4 is changed in opposite directions: TgWnk4(PHAII) mice have higher blood pressure, hyperkalemia, hypercalciuria and marked hyperplasia of the distal convoluted tubule (DCT), whereas the opposite is true in TgWnk4(WT) mice. Genetic deficiency for the Na-Cl cotransporter of the DCT (NCC) reverses phenotypes seen in TgWnk4(PHAII) mice, demonstrating that the effects of the PHAII mutation are due to altered NCC activity. These findings establish that Wnk4 is a molecular switch that regulates the balance between NaCl reabsorption and K+ secretion by altering the mass and function of the DCT through its effect on NCC. 相似文献
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A genome-wide association study identifies alleles in FGFR2 associated with risk of sporadic postmenopausal breast cancer 总被引:28,自引:0,他引:28
Hunter DJ Kraft P Jacobs KB Cox DG Yeager M Hankinson SE Wacholder S Wang Z Welch R Hutchinson A Wang J Yu K Chatterjee N Orr N Willett WC Colditz GA Ziegler RG Berg CD Buys SS McCarty CA Feigelson HS Calle EE Thun MJ Hayes RB Tucker M Gerhard DS Fraumeni JF Hoover RN Thomas G Chanock SJ 《Nature genetics》2007,39(7):870-874
We conducted a genome-wide association study (GWAS) of breast cancer by genotyping 528,173 SNPs in 1,145 postmenopausal women of European ancestry with invasive breast cancer and 1,142 controls. We identified four SNPs in intron 2 of FGFR2 (which encodes a receptor tyrosine kinase and is amplified or overexpressed in some breast cancers) that were highly associated with breast cancer and confirmed this association in 1,776 affected individuals and 2,072 controls from three additional studies. Across the four studies, the association with all four SNPs was highly statistically significant (P(trend) for the most strongly associated SNP (rs1219648) = 1.1 x 10(-10); population attributable risk = 16%). Four SNPs at other loci most strongly associated with breast cancer in the initial GWAS were not associated in the replication studies. Our summary results from the GWAS are available online in a form that should speed the identification of additional risk loci. 相似文献