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排序方式: 共有880条查询结果,搜索用时 46 毫秒
21.
Lee KS Raymond LD Schoen B Raymond GJ Kett L Moore RA Johnson LM Taubner L Speare JO Onwubiko HA Baron GS Caughey WS Caughey B 《The Journal of biological chemistry》2007,282(50):36525-36533
Hemin (iron protoporphyrin IX) is a crucial component of many physiological processes acting either as a prosthetic group or as an intracellular messenger. Some unnatural, synthetic porphyrins have potent anti-scrapie activity and can interact with normal prion protein (PrPC). These observations raised the possibility that hemin, as a natural porphyrin, is a physiological ligand for PrPC. Accordingly, we evaluated PrPC interactions with hemin. When hemin (3-10 microM) was added to the medium of cultured cells, clusters of PrPC formed on the cell surface, and the detergent solubility of PrPC decreased. The addition of hemin also induced PrPC internalization and turnover. The ability of hemin to bind directly to PrPC was demonstrated by hemin-agarose affinity chromatography and UV-visible spectroscopy. Multiple hemin molecules bound primarily to the N-terminal third of PrPC, with reduced binding to PrPC lacking residues 34-94. These hemin-PrPC interactions suggest that PrPC may participate in hemin homeostasis, sensing, and/or uptake and that hemin might affect PrPC functions. 相似文献
22.
Siderophore uptake in bacteria and the battle for iron with the host; a bird’s eye view 总被引:1,自引:0,他引:1
Byron C. Chu Alicia Garcia-Herrero Ted H. Johanson Karla D. Krewulak Cheryl K. Lau R. Sean Peacock Zoya Slavinskaya Hans J. Vogel 《Biometals》2010,23(4):601-611
Siderophores are biosynthetically produced and secreted by many bacteria, yeasts, fungi and plants, to scavenge for ferric
iron (Fe3+). They are selective iron-chelators that have an extremely high affinity for binding this trivalent metal ion. The ferric
ion is poorly soluble but it is the form of iron that is predominantly found in oxygenated environments. Siderophore uptake
in bacteria has been extensively studied and over the last decade, detailed structural information for many of the proteins
that are involved in their transport has become available. Specifically, numerous crystal structures for outer membrane siderophore
transporters, as well as for soluble periplasmic siderophore-binding proteins, have been reported. Moreover, unique siderophore-binding
proteins have recently been serendipitously discovered in humans, and the structures of some of their siderophore-complexes
have been characterized. The binding pockets for different ferric-siderophores in these proteins have been described in great
molecular detail. In addition to highlighting this structural information, in this review paper we will also briefly discuss
the relevant chemical properties of iron, and provide a perspective on our current understanding of the human and bacterial
iron uptake pathways. Potential clinical uses of siderophores will also be discussed. The emerging overall picture is that
iron metabolism plays an extremely important role during bacterial infections. Because levels of free ferric iron in biological
systems are always extremely low, there is serious competition for iron and for ferric-siderophores between pathogenic bacteria
and the human or animal host. 相似文献
23.
Penelope Koraka Byron E. E. Martina Jouke M. Roose Pieter-Paul A. M. van Thiel Geert van Amerongen Thijs Kuiken Albert D. M. E. Osterhaus 《PLoS pathogens》2012,8(5)
A fatal human case of Duvenhage virus (DUVV) infection in a Dutch traveller who had returned from Kenya was reported in 2007. She exhibited classical symptoms of rabies encephalitis with distinct pathological findings. In the present study we describe the isolation and characterization of DUVV in vitro and its passage in BALB/c mice. The virus proved to be neuroinvasive in both juvenile and adult mice, resulting in about 50% lethality upon peripheral infection. Clinical signs in infected mice were those of classical rabies. However, the distribution of viral antigen expression in the brain differed from that of classical rabies virus infection and neither inclusion bodies nor neuronal necrosis were observed. This is the first study to describe the in vitro and in vivo isolation and characterization of DUVV. 相似文献
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John J. Malinowski Bruce L. Grasberger Gary Trakshel Edward E. Huston Tracey M. Banks Patricia G. Brake Richard B. Ciccarelli Barry N. Jones James A. Koehn Diane Kratz Nicole Lundberg Panayiotis E. Stevis Carla T. Helaszek Mark A. Ator Angela M. Small Wood Travis Stams Byron Rubin Richard S. Alexander 《Protein science : a publication of the Protein Society》1995,4(10):2149-2155
26.
Tn3 resolvase is a site-specific DNA recombinase, which catalyzes strand exchange in a synaptic complex containing twelve resolvase subunits and two res sites. Hyperactive mutants of resolvase can form a simpler complex (X synapse) containing a resolvase tetramer and two shorter DNA segments at which strand exchange takes place (site I). We have solved the low-resolution solution structure of the purified, catalytically competent X synapse from small-angle neutron and X-ray scattering data, using methods in which the data are fitted with models constructed by rigid body transformations of a published crystallographic structure of a resolvase dimer bound to site I. Our analysis reveals that the two site I fragments are on the outside of a resolvase tetramer core and provides some information on the quaternary structure of the tetramer. We discuss implications of our structure for the architecture of the natural synaptic complex and the mechanism of strand exchange. 相似文献
27.
Caroline S Fortunato Alexander Eiler Lydie Herfort Joseph A Needoba Tawnya D Peterson Byron C Crump 《The ISME journal》2013,7(10):1899-1911
Bacterioplankton communities are deeply diverse and highly variable across space and time, but several recent studies demonstrate repeatable and predictable patterns in this diversity. We expanded on previous studies by determining patterns of variability in both individual taxa and bacterial communities across coastal environmental gradients. We surveyed bacterioplankton diversity across the Columbia River coastal margin, USA, using amplicon pyrosequencing of 16S rRNA genes from 596 water samples collected from 2007 to 2010. Our results showed seasonal shifts and annual reassembly of bacterioplankton communities in the freshwater-influenced Columbia River, estuary, and plume, and identified indicator taxa, including species from freshwater SAR11, Oceanospirillales, and Flavobacteria groups, that characterize the changing seasonal conditions in these environments. In the river and estuary, Actinobacteria and Betaproteobacteria indicator taxa correlated strongly with seasonal fluctuations in particulate organic carbon (ρ=−0.664) and residence time (ρ=0.512), respectively. In contrast, seasonal change in communities was not detected in the coastal ocean and varied more with the spatial variability of environmental factors including temperature and dissolved oxygen. Indicator taxa of coastal ocean environments included SAR406 and SUP05 taxa from the deep ocean, and Prochlorococcus and SAR11 taxa from the upper water column. We found that in the Columbia River coastal margin, freshwater-influenced environments were consistent and predictable, whereas coastal ocean community variability was difficult to interpret due to complex physical conditions. This study moves beyond beta-diversity patterns to focus on the occurrence of specific taxa and lends insight into the potential ecological roles these taxa have in coastal ocean environments. 相似文献
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30.
Helena C. Kraemer Byron Alexander Cathy Clark Curt Busse David Riss 《Primates; journal of primatology》1977,18(4):825-833
A method is suggested to evaluate on an empirical basis sampling plans for the longitudinal study of primate behavior in those
very common situations in which the mathematical structure of behavior is unknown. The method is based on a randomization
procedure applied to a pilot sample of the behavior organized so that cost of implementation of a sampling plan can be evaluated
vis á vis the sampling error intrinsic to the plan. 相似文献