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1.
Structural relatedness of lysis proteins from colicinogenic plasmids and icosahedral coliphages 总被引:4,自引:0,他引:4
The host-lysis-inducing functions of phi X174 protein E and MS2 protein L
were recently shown to reside on the N-terminal and C-terminal halves of
the two respective lysis proteins. In the present study it is shown that
the small lysis proteins encoded in various colicinogenic plasmids share
local sequence similarities and certain structural characteristics with the
essential peptides of their coliphage-coded counterparts. Despite their
dissimilar sizes and origins, it is suggested that the colicinogenic lysis
proteins are functionally analogous and evolutionarily related to those of
icosahedral single- stranded DNA and RNA phages.
相似文献
2.
Cecilia PC Soh Alastair SR Donald James Feeney Walter TJ Morgan Winifred M Watkins 《Glycoconjugate journal》1989,6(3):319-332
The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and1H-500 MHz NMR spectroscopy. In Sda serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity. 相似文献
3.
The daily and seasonal distribution of airborne fungal particles was recorded in a high altitude tropical zone. Sampling was
carried out in the southern part of Mexico City. An Andersen air sampler was used over a period of six months. Ten minutes
sampling for each set of plates was done at fixed schedule: 07:30, 14:00 and 19:00 hours. The sampler was placed 10 m above
the ground. Daily variation was found to be associated with the season, weather and atmospheric stability. The highest value
of mold counts (3195 CFU m−3) was recorded in the evening on October, a transitional month between the rainy and the dry seasons, the lowest (45 CFU m−3) at noon during the rainy season. Mold counts were significantly correlated with temperature, having negative signs both
in the morning and at noon, and being positive in the evening. The abundance of only three genera was recorded.Cladosporium, was isolated more frequently, and its abundance at 14:00 h was of 38%;Alternaria represented 4.0%, at 14:00 h, andAspergillus 3.0% at 7:30 h. Fifteen species belonging to the latter genera were identified and most of them are considered as opportunistic
molds of clinical significance. 相似文献
4.
Overproduction of threonine by Saccharomyces cerevisiae mutants resistant to hydroxynorvaline.
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In this work, we isolated and characterized mutants that overproduce threonine from Saccharomyces cerevisiae. The mutants were selected for resistance to the threonine analog alpha-amino-beta-hydroxynorvalerate (hydroxynorvaline), and, of these, the ones able to excrete threonine to the medium were chosen. The mutant strains produce between 15 and 30 times more threonine than the wild type does, and, to a lesser degree, they also accumulate isoleucine. Genetic and biochemical studies have revealed that the threonine overproduction is, in all cases studied, associated with the presence in the strain of a HOM3 allele coding for a mutant aspartate kinase that is totally or partially insensitive to feedback inhibition by threonine. This enzyme seems, therefore, to be crucial in the regulation of threonine biosynthesis in S. cerevisiae. The results obtained suggest that this strategy could be efficiently applied to the isolation of threonine-overproducing strains of yeasts other than S. cerevisiae, even those used industrially. 相似文献
5.
Phillip A Patten Russell J Howard Willem PC Stemmer 《Current opinion in biotechnology》1997,8(6):724-733
DNA shuffling is a practical process for directed molecular evolution which uses recombination to dramatically accelerate the rate at which one can evolve genes. Single and multigene traits that require many mutations for improved phenotypes can be evolved rapidly. DNA shuffling technology has been significantly enhanced in the past year, extending its range of applications to small molecule pharmaceuticals, pharmaceutical proteins, gene therapy vehicles and transgenes, vaccines and evolved viruses for vaccines, and laboratory animal models. 相似文献
6.
Analysis of Immunoprecipitated Surface Glycoproteins in Measles Virions and in Membranes of Infected Cells
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Measles viral envelope proteins were immune precipitated from membranes of infected cells and from purified virus and analyzed by polyacrylamide gel electrophoresis. Under reducing conditions, specific precipitates contained two major polypeptide bands, designated virus glycopeptides 1 and 2 (VGP-1 and VGP-2). Both polypeptides appeared to be glycosylated, as indicated by their incorporation of [14C]glucosamine in infected cells. VGP-2 appeared as a single band in specific precipitates of infected cells and as a double band in precipitates of purified virus. Trypsin treatment of infected cells showed that reduced VGP-2 may be composed of two unrelated polypeptides. One may be F1, which is unglycosylated, and the other may correspond to the proteolytic cleavage product of VGP-1, which is glycosylated. The relation of VGP-1 and VGP-2 to smaller surface antigens (X and Y) obtained by tryptic treatment of infected cells remains to be elucidated. In cells taken at various times postinfection and analyzed for viral membrane proteins, VGP-1 was detected at all times, indicating that the input virus VGP-1 was inserted into the cell and could not be differentiated from newly synthesized VGP-1. VGP-2 was not detectable before 24 h postinfection. In precipitates of cells 4 h postinfection and of infected cells incubated at pH 5.8, an additional polypeptide band migrated immediately ahead of VGP-1. We conclude that VGP-2 (molecular weight, 42,000) possibly consists of two components, one of which is the tryptic cleavage product of VGP-1 and the other of which is the unglycosylated polypeptide, F1. 相似文献
7.
Cluster Computing - This paper proposes a new version of the power of two choices, SQ(d), load balancing algorithm. This new algorithm improves the performance of the classical model based on the... 相似文献
8.
Julian A. Villalba Yushi Liu Mauyuri K. Alvarez Luisana Calderon Merari Canache Gaudymar Cardenas Berenice Del Nogal Howard E. Takiff Jacobus H. De Waard 《PloS one》2013,8(12)
Background
Warao Amerindians, who inhabit the Orinoco Delta, are the second largest indigenous group in Venezuela. High Warao general mortality rates were mentioned in a limited study 21 years ago. However, there have been no comprehensive studies addressing child survival across the entire population.Objectives
To determine the Child Survival-Index (CSI) (ratio: still-living children/total-live births) in the Warao population, the principal causes of childhood death and the socio-demographic factors associated with childhood deaths.Methods
We conducted a cross-sectional epidemiological survey of 688 women from 97 communities in 7 different subregions of the Orinoco Delta. Data collected included socio-demographic characteristics and the reproductive history of each woman surveyed. The multidimensional poverty index (MPI) was used to classify the households as deprived across the three dimensions of the Human Development Index. Multivariable linear regression and Generalized Linear Model Procedures were used to identify socioeconomic and environmental characteristics statistically associated with the CSI.Findings
The average CSI was 73.8% ±26. The two most common causes of death were gastroenteritis/diarrhea (63%) and acute respiratory tract Infection/pneumonia (18%). Deaths in children under five years accounted for 97.3% of childhood deaths, with 54% occurring in the neonatal period or first year of life. Most of the women (95.5%) were classified as multidimensionally poor. The general MPI in the sample was 0.56. CSI was negatively correlated with MPI, maternal age, residence in a traditional dwelling and profession of the head of household other than nurse or teacher.Conclusions
The Warao have a low CSI which is correlated with MPI and maternal age. Infectious diseases are responsible for 85% of childhood deaths. The low socioeconomic development, lack of infrastructure and geographic and cultural isolation suggest that an integrated approach is urgently needed to improve the child survival and overall health of the Warao Amerindians. 相似文献9.
10.
Eva Veronesi Frank Antony Simon Gubbins Nick Golding Alison Blackwell Peter PC. Mertens Joe Brownlie Karin E. Darpel Philip S. Mellor Simon Carpenter 《PloS one》2013,8(8)