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861.
The genome sequence of Yersinia pestis bacteriophage phiA1122 reveals an intimate history with the coliphage T3 and T7 genomes 下载免费PDF全文
Garcia E Elliott JM Ramanculov E Chain PS Chu MC Molineux IJ 《Journal of bacteriology》2003,185(17):5248-5262
The genome sequence of bacteriophage phiA1122 has been determined. phiA1122 grows on almost all isolates of Yersinia pestis and is used by the Centers for Disease Control and Prevention as a diagnostic agent for the causative agent of plague. phiA1122 is very closely related to coliphage T7; the two genomes are colinear, and the genome-wide level of nucleotide identity is about 89%. However, a quarter of the phiA1122 genome, one that includes about half of the morphogenetic and maturation functions, is significantly more closely related to coliphage T3 than to T7. It is proposed that the yersiniophage phiA1122 recombined with a close relative of the Y. enterocolitica phage phiYeO3-12 to yield progeny phages, one of which became the classic T3 coliphage of Demerec and Fano (M. Demerec and U. Fano, Genetics 30:119-136, 1945). 相似文献
862.
Armengaud J Fernandez B Chaumont V Rollin-Genetet F Finet S Marchetti C Myllykallio H Vidaud C Pellequer JL Gribaldo S Forterre P Gans P 《The Journal of biological chemistry》2003,278(33):31078-31087
Although coenzymeA (CoA) is essential in numerous metabolic pathways in all living cells, molecular characterization of the CoA biosynthetic pathway in Archaea remains undocumented. Archaeal genomes contain detectable homologues for only three of the five steps of the CoA biosynthetic pathway characterized in Eukarya and Bacteria. In case of phosphopantetheine adenylyltransferase (PPAT) (EC 2.7.7.3), the putative archaeal enzyme exhibits significant sequence similarity only with its eukaryotic homologs, an unusual situation for a protein involved in a central metabolic pathway. We have overexpressed in Escherichia coli, purified, and characterized this putative PPAT from the hyperthermophilic archaeon Pyrococcus abyssi (PAB0944). Matrix-assisted laser desorption ionization-time of flight mass spectrometry and high performance liquid chromatography measurements are consistent with the presence of a dephospho-CoA (dPCoA) molecule tightly bound to the polypeptide. The protein indeed catalyzes the synthesis of dPCoA from 4'-phosphopantetheine and ATP, as well as the reverse reaction. The presence of dPCoA stabilizes PAB0944, as it induces a shift from 76 to 82 degrees C of the apparent Tm measured by differential scanning microcalorimetry. Potassium glutamate was found to stabilize the protein at 400 mm. The enzyme behaves as a monomeric protein. Although only distantly related, secondary structure prediction indicates that archaeal and eukaryal PPAT belong to the same nucleotidyltransferase superfamily of bacterial PPAT. The existence of operational proteins highly conserved between Archaea and Eukarya involved in a central metabolic pathway challenge evolutionary scenarios in which eukaryal operational proteins are strictly of bacterial origin. 相似文献
863.
Mould AP Symonds EJ Buckley PA Grossmann JG McEwan PA Barton SJ Askari JA Craig SE Bella J Humphries MJ 《The Journal of biological chemistry》2003,278(41):39993-39999
The structural basis of the interaction of integrin heterodimers with their physiological ligands is poorly understood. We have used solution x-ray scattering to visualize the head region of integrin alpha 5 beta 1 in an inactive (Ca2+-occupied) state, and in complex with a fragment of fibronectin containing the RGD and synergy recognition sequences. Shape reconstructions of the data have been interpreted in terms of appropriate molecular models. The scattering data suggest that the head region undergoes no gross conformational changes upon ligand binding but do lend support to a proposed outward movement of the hybrid domain in the beta subunit. Fibronectin is observed to bind across the top of the head region, which contains an alpha subunit beta-propeller and a beta subunit vWF type A domain. The model of the complex indicates that the synergy region binds on the side of the beta-propeller domain. In support of this suggestion, mutagenesis of a prominent loop region on the side of the propeller identifies two residues (Tyr208 and Ile210) involved in recognition of the synergy region. Our data provide the first view of a complex between an integrin and a macromolecular ligand in solution, at a nominal resolution of approximately 10 A. 相似文献
864.
Cytoplasmic serine hydroxymethyltransferase (cSHMT) is a tetrameric, pyridoxal phosphate (PLP)-dependent enzyme that catalyzes the reversible interconversion of serine and tetrahydrofolate to glycine and methylenetetrahydrofolate. The enzyme has four active sites and is best described as a dimer of obligate dimers. Each monomeric subunit within the obligate dimer contributes catalytically important amino acid residues to both active sites. To investigate the interchange of subunits among cSHMT tetramers, a dominant-negative human cSHMT enzyme (DNcSHMT) was engineered by making three amino acid substitutions: K257Q, Y82A, and Y83F. Purified recombinant DNcSHMT protein was catalytically inactive and did not bind 5-formyltetrahydrofolate. Coexpression of the cSHMT and DNcSHMT proteins in bacteria resulted in the formation of heterotetramers with a cSHMT/DNcSHMT subunit ratio of 1. Characterization of the cSHMT/DNcSHMT heterotetramers indicates that DNcSHMT and cSHMT monomers randomly associate to form tetramers and that cSHMT/DNcSHMT obligate dimers are catalytically inactive. Incubation of recombinant cSHMT protein with recombinant DNcSHMT protein did not result in the formation of hetero-oligomers, indicating that cSHMT subunits do not exchange once the tetramer is assembled. However, removal of the active site PLP cofactor does permit exchange of obligate dimers among preformed cSHMT and DNcSHMT tetramers, and the formation of heterotetramers from cSHMT and DNcSHMT homodimers does not affect the activity of the cSHMT homodimers. The results of these studies demonstrate that PLP inhibits dimer exchange among cSHMT tetramers and suggests that cellular PLP concentrations may influence the stability of cSHMT protein in vivo. 相似文献
865.
Delmas C Aragou N Poussard S Cottin P Darbon JM Manenti S 《The Journal of biological chemistry》2003,278(14):12443-12451
We investigated the status and the regulation of the cyclin-dependent kinases (CDK) inhibitor p27(Kip1) in a choroidal melanoma tumor-derived cell line (OCM-1). By contrast to normal choroidal melanocytes, the expression level of p27(Kip1) was low in these cells and the mitogen-activated protein (MAP) kinase pathway was constitutively activated. Genetic or chemical inhibition of this pathway induced p27(Kip1) accumulation, whereas MAP kinase reactivation triggered a down-regulation of p27(Kip1) that could be partially reversed by calpain inhibitors. In good accordance, ectopic expression of the cellular calpain inhibitor calpastatin led to an increase of endogenous p27(Kip1) expression. In vitro, p27(Kip1) was degraded by calpains, and OCM-1 cell extracts contained a calcium-dependent p27(Kip1) degradation activity. MAP kinase inhibition partially inhibited both calpain activity and calcium-dependent p27(Kip1) degradation by cellular extracts. Immunofluorescence labeling and subcellular fractionation revealed that p27(Kip1) was in part localized in the cytoplasmic compartment of OCM-1 cells but not of melanocytes, and accumulated into the nucleus upon MAP kinase inhibition. MAP kinase activation triggered a cytoplasmic translocation of the protein, as well as a change in its phosphorylation status. This CRM-1-dependent cytoplasmic translocation was necessary for MAP kinase- and calpain-dependent degradation. Taken together, these data suggest that in tumor-derived cells, p27(Kip1) could be degraded by calpains through a MAP kinase-dependent process, and that abnormal cytoplasmic localization of the protein, probably linked to modifications of its phosphorylation state, could be involved in this alternative mechanism of degradation. 相似文献
866.
Jean-Paul Wathelet Renato Iori Onofrio Leoni Patrick Rollin Nicolas Mabon Michel Marlier Sandro Palmieri 《Biotechnology letters》2001,23(6):443-446
Glucosinolates, natural compounds found in Brassicaceae, can easily be transformed into desulfo-glucosinolates by action of Helix pomatia sulfatase. The recombinant -O-glucosidase from Caldocellum saccharolyticum does not catalyse glucosinolate degradation but can hydrolyse desulfo-glucosinolates (thio-d-glucosidic substrates) to produce the corresponding pure nitriles, including valuable homochiral representatives. 相似文献
867.
Osinga R Kleijn R Groenendijk E Niesink P Tramper J Wijffels RH 《Marine biotechnology (New York, N.Y.)》2001,3(6):544-554
The rate of food particle uptake of the tropical sponge Pseudosuberites aff. andrewsi was studied in relation to particle concentrations and particle size. A range of different concentrations of either the marine
microalga Dunaliella tertiolecta (∼5–8 μm) or the marine cyanobacterium Synechococcus sp. (∼1 μm) was supplied to the sponges. D. tertiolecta had a pronounced effect on the filtration activity of the sponges: at concentrations higher than approximately 4 × 105 cells/cm3, the filtration rates dropped dramatically. Such a clear effect was not found for Synechococcus sp. The results further showed that the maximal amount of food (when expressed in organic carbon) that can be taken up per
cubic centimeter of sponge volume per unit of time should in principle be sufficient to enable growth (irrespective of the
food particle type). At the maximal food particle concentration that did not affect the filtration rates, the uptake of organic
carbon is already highly in excess of the amount of organic carbon that the sponges need to cope with their respiratory demand.
Based on these findings, a series of growth experiments was carried out in which the sponges were subjected to a constant
concentration of different types of food particles (Synechococcus sp. and the microalgae Chlorella sorokiniana and Nannochloropsis sp). Although initial growth was sometimes observed, continuous growth at a constant rate could not be obtained. It is concluded
that qualitative aspects of feeding rather than quantitative aspects are the key to successful in vivo sponge culture.
Received December 20, 2000; accepted March 26, 2001 相似文献
868.
Shum PW Peet NP Weintraub PM Le TB Zhao Z Barbone F Cashman B Tsay J Dwyer S Loos PC Powers EA Kropp K Wright PS Bitonti A Dumont J Borcherding DR 《Nucleosides, nucleotides & nucleic acids》2001,20(4-7):1067-1078
Cyclin-dependent kinases (CDKs) belong to a class of enzymes that control the ability of a cell to enter into and proceed through the cell division cycle. Using purine as a scaffold, we have synthesized a number of nanomolar inhibitors of CDK-2/cyclin E. In this report, the synthesis of a series of piperidine-substituted purine analogs will be presented, as well as some of their in vitro and in vivo biological effects. 相似文献
869.
870.
David L. Steer Rebecca A. Lew Patrick Perlmutter A. Ian Smith Marie-Isabel Aguilar 《Letters in Peptide Science》2001,8(3-5):241-246
The use of -amino acids as peptidomimetics has emerged in recent years with significant potential in a number of applications. The incorporation of -amino acids has been successful in creating peptidomimetics that not only have potent biological activity, but are also resistant to proteolysis. This article reviews the recent applications of -amino acids in the design of protease and peptidase inhibitors. Given their structural diversity, together with the ease of synthesis and incorporation into peptide sequences using standard solid-phase peptide synthesis techniques, -amino acids have the potential to form a new platform technology for peptidomimetic design and synthesis. 相似文献