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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.
Site-specific recombination by mutants of Tn21 resolvase with DNA recognition functions from Tn3 resolvase 总被引:3,自引:0,他引:3
The resolvases from the transposons Tn3 and Tn21 are homologous proteins but they possess distinct specificities for the DNA sequence at their respective res sites. The DNA binding domain of resolvase contains an amino acid sequence that can be aligned with the helix-turn-helix motif of other DNA binding proteins. Mutations in the gene for Tn21 resolvase were made by replacing the section of DNA that codes for the helix-turn-helix with synthetic oligonucleotides. Each mutation substituted one amino acid in Tn21 resolvase with either the corresponding residue from Tn3 resolvase or a residue that lacks hydrogen bonding functions. The ability of these proteins to mediate recombination between res sites from either Tn21 or Tn3 was measured in vivo and in vitro. With one exception, where a glutamate residue had been replaced by leucine, the activity of these mutants was similar to that of wild-type Tn21 resolvase. A further mutation was made in which the complete recognition helix of Tn21 resolvase was replaced with that from Tn3 resolvase. This protein retained activity in recombining Tn21 res sites, though at a reduced level relative to wild-type; the reduction can be assigned entirely to weakened binding to this DNA. Neither this mutant nor any other derivative of Tn21 resolvase had any detectable activity for recombination between res sites from Tn3. The exchange of this section of amino acid sequence between the two resolvases is therefore insufficient to alter the DNA sequence specificity for recombination. 相似文献
4.
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
5.
Abstract An improved alternative synthesis of 4-cyano-2-butenyldeoxy nucleosidephosphoramidites in > 100g quantities is described via reaction of the phosphordiamidites with 4-cyano-2-buten-1-ol. 相似文献
6.
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)
Background
Culicoides biting midges (Diptera: Ceratopogonidae) are the biological vectors of globally significant arboviruses of livestock including bluetongue virus (BTV), African horse sickness virus (AHSV) and the recently emerging Schmallenberg virus (SBV). From 2006–2009 outbreaks of BTV in northern Europe inflicted major disruption and economic losses to farmers and several attempts were made to implicate Palaearctic Culicoides species as vectors. Results from these studies were difficult to interpret as they used semi-quantitative RT-PCR (sqPCR) assays as the major diagnostic tool, a technique that had not been validated for use in this role. In this study we validate the use of these assays by carrying out time-series detection of BTV RNA in two colony species of Culicoides and compare the results with the more traditional isolation of infectious BTV on cell culture.Methodology/Principal Findings
A BTV serotype 1 strain mixed with horse blood was fed to several hundred individuals of Culicoides sonorensis (Wirth & Jones) and C. nubeculosus (Mg.) using a membrane-based assay and replete individuals were then incubated at 25°C. At daily intervals 25 Culicoides of each species were removed from incubation, homogenised and BTV quantified in each individual using sqPCR (Cq values) and virus isolation on a KC-C. sonorensis embryonic cell line, followed by antigen enzyme-linked immunosorbent assay (ELISA). In addition, comparisons were also drawn between the results obtained with whole C. sonorensis and with individually dissected individuals to determine the level of BTV dissemination.Conclusions/Significance
Cq values generated from time-series infection experiments in both C. sonorensis and C. nubeculosus confirmed previous studies that relied upon the isolation and detection of infectious BTV. Implications on the testing of field-collected Culicoides as potential virus vectors by PCR assays and the use of such assays as front-line tools for use in diagnostic laboratories in this role are discussed. 相似文献7.
Phylogenetic relationships were determined for 76 partial P-element
sequences from 14 species of the melanogaster species group within the
Drosophila subgenus Sophophora. These results are examined in the context
of the phylogeny of the species from which the sequences were isolated.
Sequences from the P-element family fall into distinct subfamilies, or
clades, which are often characteristic for particular species subgroups.
When examined locally among closely related species, the evolution of P
elements is characterized by vertical transmission, whereby the P-element
phylogeny traces the species phylogeny. On a broader scale, however, the
P-element phylogeny is not congruent with the species phylogeny. One
feature of P-element evolution in the melanogaster group is the presence of
more than one P-element subfamily, differing by as much as 36%, in the
genomes of some species. Thus, P elements from several individual species
are not monophyletic, and a likely explanation for the incongruence between
P-element and species phylogenies is provided by the comparison of
paralogous sequences. In certain instances, horizontal transfer seems to be
a valid alternative explanation for lack of congruence between species and
P-element phylogenies. The canonical P-element subfamily, which represents
the active, autonomous transposable element, is restricted to D.
melanogaster. Thus, its origin clearly lies outside of the melanogaster
species group, consistent with the earlier conclusion of recent horizontal
transfer.
相似文献
8.
9.
10.
Carl PC Chen Chih-Chin Hsu Wen-Lin Yeh Hsiu-Chu Lin Sen-Yung Hsieh Shih-Cherng Lin Tai-Tzung Chen Max JL Chen Simon FT Tang 《Proteome science》2011,9(1):1-10