共查询到20条相似文献,搜索用时 46 毫秒
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A Kuninaka 《Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme》1985,30(11):1253-1256
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Masao Fujimoto Akira Kuninaka Hiroshi Yoshino 《Bioscience, biotechnology, and biochemistry》2013,77(7):1121-1124
Properties of nuclease P1-malonogalactan complex (P1-MG) were compared with those of the polysaccharide-free nuclease P1. Significant difference was not observed between them in phosphomonoester splitting activity, but marked differences were observed in nucleolytic activity as follows: (1) The pH optima of P1-MG for RNA and heat-denatured DNA were lower than those of nuclease P1. (2) At lower than 0.001 of ionic strength, RNA and heat- denatured DNA were attacked hardly by P1-MG, but attacked well by nuclease P1. (3) The increase in hydrolysis rate of RNA or heat-denatured DNA with an elevation of temperature from 37°C to 70°C was not so marked in P1-MG as compared with nuclease P1. (4) P1-MG hydrolyzed polynucleotides, especially native DNA, much slower than nuclease P1.Influence of ionic strength, pH and temperature on the nucleolytic activity of nuclease P1-galactan (P1-G), which was prepared by demalonylating P1-MG enzymatically, was similar to that of nuclease P1, except that the activity of P1-G for native DNA was much lower than nuclease P1. 相似文献
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Abstract The lipopolysaccharide (LPS) of Klebsiella pneumoniae was altered as a consequence of P1CM ts lysogeny by a reduction in size to a heptose-deficient form. P1CM ts lysogens were sensitive to P1 vir and K. pneumoniae phages. P1CM ts -cured strains were sensitive to P1CM ts and P1 vir and P1CM ts lysogens were likewise able to inactivate P1 vir . Concomitantly, the wild type showed a smooth LPS, while P1CM ts lysogens and P1CM ts -cured strains showed a rough LPS (heptose-deficient form).
It is suggested that P1CM ts and P1 vir , are only able to infect K. pneumoniae by selecting a LPS-deficient mutant (chemotype Re). 相似文献
It is suggested that P1CM ts and P1 vir , are only able to infect K. pneumoniae by selecting a LPS-deficient mutant (chemotype Re). 相似文献
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Ax A Schaal W Vrang L Samuelsson B Hallberg A Karlén A 《Bioorganic & medicinal chemistry》2005,13(3):755-764
Previous studies of HIV protease inhibitors have shown that it is possible to elongate the P1/P1' sidechains to reach the S3/S3' binding sites. By analogy, we expected that it would be possible to design inhibitors reaching between the S1/S1' and S2/S2' binding sites. Molecular modeling suggested that this could be achieved with appropriate ortho-substitution of the P2/P2' benzyl groups in our cyclic sulfamide inhibitors. Four different spacer groups were investigated. The compounds were smoothly prepared from tartaric acid in five steps and exhibit low to moderate activity, the most potent inhibitor possessing a Ki value of 0.53 microM. 相似文献
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《Cellular signalling》2014,26(7):1576-1588
The sphingosine-1-phosphate (S1P) type 1 receptor (S1P1R) is a novel therapeutic target in lymphocyte-mediated autoimmune diseases. S1P1 receptor desensitization caused by synthetic S1P1 receptor agonists prevents T-lymphocyte egress from secondary lymphoid organs into the circulation. The selective S1P1 receptor agonist ponesimod, which is in development for the treatment of autoimmune diseases, efficiently reduces peripheral lymphocyte counts and displays efficacy in animal models of autoimmune disease. Using ponesimod and the natural ligand S1P, we investigated the molecular mechanisms leading to different signaling, desensitization and trafficking behavior of S1P1 receptors. In recombinant S1P1 receptor-expressing cells, ponesimod and S1P triggered Gαi protein-mediated signaling and β-arrestin recruitment with comparable potency and efficiency, but only ponesimod efficiently induced intracellular receptor accumulation. In human umbilical vein endothelial cells (HUVEC), ponesimod and S1P triggered translocation of the endogenous S1P1 receptor to the Golgi compartment. However, only ponesimod treatment caused efficient surface receptor depletion, receptor accumulation in the Golgi and degradation. Impedance measurements in HUVEC showed that ponesimod induced only short-lived Gαi protein-mediated signaling followed by resistance to further stimulation, whereas S1P induced sustained Gαi protein-mediated signaling without desensitization. Inhibition of S1P lyase activity in HUVEC rendered S1P an efficient S1P1 receptor internalizing compound and abrogated S1P-mediated sustained signaling. This suggests that S1P lyase – by facilitating S1P1 receptor recycling – is essential for S1P-mediated sustained signaling, and that synthetic agonists are functional antagonists because they are not S1P lyase substrates. 相似文献
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Kono M Mi Y Liu Y Sasaki T Allende ML Wu YP Yamashita T Proia RL 《The Journal of biological chemistry》2004,279(28):29367-29373
Sphingosine-1-phosphate (S1P) elicits diverse cellular responses through a family of G-protein-coupled receptors. We have shown previously that genetic disruption of the S1P(1) receptor, the most widely expressed of the family, results in embryonic lethality because of its key role within endothelial cells in regulating the coverage of blood vessels by vascular smooth muscle cells. To understand the physiologic functions of the two other widely expressed S1P receptors, we generated S1P(2) and S1P(3) null mice. Neither the S1P(2) null mice nor the S1P(3) null mice exhibited significant embryonic lethality or obvious phenotypic abnormalities. To unmask possible overlapping or collaborative functions between the S1P(1), S1P(2), and S1P(3) receptors, we examined embryos with multiple S1P receptor mutations. We found that S1P(1) S1P(2) double null and S1P(1) S1P(2) S1P(3) triple null embryos displayed a substantially more severe vascular phenotype than did embryos with only S1P(1) deleted. We also found partial embryonic lethality and vascular abnormalities in S1P(2) S1P(3) double null embryos. Our results indicate that the S1P(1), S1P(2) and S1P(3) receptors have redundant or cooperative functions for the development of a stable and mature vascular system during embryonic development. 相似文献
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Plaque forming specialized transducing phage P1: Isolation of P1CmSmSu, a precursor of P1Cm 总被引:6,自引:0,他引:6
Summary
E. coli strains lysogenic for various types of P1-R hybrids were isolated. These carry all the essential genes for vegetative phage production and lysogenization including P1 immunity and P1 incompatibility, together with drug resistance genes derived from the R plasmid NR1. In particular, P1Cm and P1CmSmSu derivatives were studied. When strains lysogenic for these phages were induced in the absence of helper phage, yields of phage particles as high as with wild type P1 were obtained. All P1Cm phages isolated were of plaque forming type and usually every plaque contained Cmr lysogens. Lysates of P1CmSmSu lysogens transduced CmrSmrSur at high frequency and they formed plaques with an efficiency of 10-4 to 10-2 per phage particle. Only a minority of these plaques contained drug resistant bacteria. CmrSmrSur transductants isolated from bacteria infected at a high multiplicity with phage P1CmSmSu were lysogens for the original P1CmSmSu. In contrast, CmrSmrSur transductants isolated after infection at low multiplicity appeared to carry the CmrSmrSur markers integrated into the host chromosome. The results described suggest that P1CmSmSu prophages carry the resistance genes transposed into the P1 genome without in principle causing a loss of essential gene functions. However, since these prophages are longer than the wild type P1 genome, the DNA packaged into phage particles has a reduced redundancy which seriously affects the reproduction and lysogenization abilities.Plaque forming P1Cm can be obtained from P1CmSmSu. Thus, P1CmSmSu is a precursor of P1Cm. P1Cm is also obtainable from P1 and NR1 under the recA
- condition. The mechanism of formation of plaque forming P1Cm is discussed. 相似文献
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M Velleman M Heirich A Günther H Schuster 《The Journal of biological chemistry》1990,265(30):18511-18517
Bacteriophage P1 encodes a tripartite immunity system composed of the immC, immI, and immT region. Their basic genetic elements are the c1 repressor of lytic functions, the c4 repressor which negatively regulates antirepressor synthesis, and the bof gene, respectively. The function of the latter will be described here. We have cloned and sequenced the bof gene from P1 wild type and a P1 bof amber mutant. Based on the position of a TAG codon of the bof amber mutant the bof wild type gene was localized. It starts with a TTG codon, comprises 82 codons, and is preceded by a promoter structure. The bof protein (Mr = 7500) was overproduced in Escherichia coli from a bof recombinant plasmid and was purified to near homogeneity. The N-terminal amino acids predicted from the DNA sequence of the bof gene were confirmed by sequence analysis of the bof protein. Using a DNA mobility shift assay, we show that bof protein enhances the binding of c1 repressor to the operator of the c1 gene. In accordance with this result, in transformants of Escherichia coli, containing both a bof- and a c1-encoding plasmid, c1 expression is down-regulated. We conclude that bof acts as a modulator protein in the repression of a multitude of c1-controlled operators in the P1 genome. 相似文献
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Curing of P1 prophage from Escherichia coli K-12 recA(P1) lysogens superinfected with P1 bacteriophage.
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Curing of the P1 plasmid prophage in recA(P1) lysogens by superinfection with another P1 phage was specific and independent of immunity and incompatibility expression. 相似文献
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Sphingosine 1-phosphate (S1P) receptor subtypes S1P1 and S1P3, respectively, regulate lymphocyte recirculation and heart rate 总被引:10,自引:0,他引:10
Sanna MG Liao J Jo E Alfonso C Ahn MY Peterson MS Webb B Lefebvre S Chun J Gray N Rosen H 《The Journal of biological chemistry》2004,279(14):13839-13848
Sphingosine 1-phosphate (S1P) influences heart rate, coronary artery caliber, endothelial integrity, and lymphocyte recirculation through five related high affinity G-protein-coupled receptors. Inhibition of lymphocyte recirculation by non-selective S1P receptor agonists produces clinical immunosuppression preventing transplant rejection but is associated with transient bradycardia. Understanding the contribution of individual receptors has been limited by the embryonic lethality of the S1P(1) knock-out and the unavailability of selective agonists or antagonists. A potent, S1P(1)-receptor selective agonist structurally unrelated to S1P was found to activate multiple signals triggered by S1P, including guanosine 5'-3-O-(thio)triphosphate binding, calcium flux, Akt and ERK1/2 phosphorylation, and stimulation of migration of S1P(1)- but not S1P(3)-expressing cells in vitro. The agonist also alters lymphocyte trafficking in vivo. Use of selective agonism together with deletant mice lacking S1P(3) receptor reveals that agonism of S1P(1) receptor alone is sufficient to control lymphocyte recirculation. Moreover, S1P(1) receptor agonist plasma levels are causally associated with induction and maintenance of lymphopenia. S1P(3), and not S1P(1), is directly implicated in sinus bradycardia. The sustained bradycardia induced by S1P receptor non-selective immunosuppressive agonists in wild-type mice is abolished in S1P(3)-/- mice, whereas S1P(1)-selective agonist does not produce bradycardia. Separation of receptor subtype usage for control of lymphocyte recirculation and heart rate may allow the identification of selective immunosuppressive S1P(1) receptor agonists with an enhanced therapeutic window. S1P(1)-selective agonists will be of broad utility in understanding cell functions in vitro, and vascular physiology in vivo, and the success of the chemical approach for S1P(1) suggests that selective tools for the resolution of function across this broad lipid receptor family are now possible. 相似文献
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The partition operon of P1 plasmid encodes two proteins, ParA and ParB, required for the faithful segregation of plasmid copies to daughter cells. The operon is followed by a centromere analog, parS, at which ParB binds. ParA, a weak ATPase, represses the par promoter most effectively in its ADP-bound form. ParB can recruit ParA to parS, stimulate its ATPase, and significantly stimulate the repression. We report here that parS also participates in the regulation of expression of the par genes. A single chromosomal parS was shown to augment repression of several copies of the par promoter by severalfold. The repression increase was sensitive to the levels of ParA and ParB and to their ratio. The increase may be attributable to a conformational change in ParA mediated by the parS-ParB complex, possibly acting catalytically. We also observed an in cis effect of parS which enhanced expression of parB, presumably due to a selective modulation of the mRNA level. Although ParB had been earlier found to spread into and silence genes flanking parS, silencing of the par operon by ParB spreading was not significant. Based upon analogies between partitioning and septum placement, we speculate that the regulatory switch controlled by the parS-ParB complex might be essential for partitioning itself. 相似文献
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Uno T Okamoto S Masuda S Imaishi H Nakamura M Kanamaru K Yamagata H El-Kady MA Kaminishi Y Itakura T 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2008,147(3):278-285
We indicated that two P450s (1A9 and 1C1) from Japanese eel (Anguilla japonica) metabolized 7-ethoxycoumarin, 7-ethoxyresorufin, and flavanone. At first, we constructed expression vectors for two types of P450 (1A9 and 1C1). The reduced CO-difference spectra of Escherichia coli cells transformed with these plasmids showed Soret peaks (450 nm) that were typical of P450s. We performed bioconversion experiments in which substrates were added directly to incubation medium. The resulting metabolite(s) were extracted and analyzed by high-performance liquid chromatography and spectrofluorometer. Incubation of 50 nmol 7-ethoxyresorufin with P450 1C1 yielded 0.773 nmol of deethylated product, whereas 50 nmol 7-ethoxycoumarin resulted in 4.76 nmol. P450 1A9 metabolized 50 nmol of 7-ethoxyresorufin and 7-ethoxycoumarin to yield 6.54 and 20.9 nmol of deethylated product, respectively. Incubation of 50 nmol flavanone with P450 1C1 yielded 1.46 nmol and 0.69 nmol of products, whereas 50 nmol flavanone with P450 1A9 resulted in 1.10 nmol. In this system, 4'-hydroxy flavanones were formed by P450 1A9 and P450 1C1. P450 1A9 also metabolized 50 nmol of 17 beta-estradiol to yield 4.25 nmol of product. In this system, 2-hydroxy estradiol was formed by P450 1A9 using 17 beta-estradiol as a substrate. This study is the first to identify the substrates that P450 1C1 and 1A9 metabolize. 相似文献
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Hu W Huang J Mahavadi S Li F Murthy KS 《Biochemical and biophysical research communications》2006,343(4):1038-1044
Sphingosine-1-phosphate regulates diverse biological processes through five receptor types, S1P(1-5). Two or more S1P receptors are usually co-expressed on target cells. We have previously shown that smooth muscle cells of the gut co-express S1P(1) and S1P(2) receptors that could mediate distinct functions. In the absence of selective agonists and antagonists, we developed siRNA constructs to silence each receptor separately. The constructs were based on identical sequences in several mammalian species. A lentiviral vector-based system was used to deliver siRNA into HEK293T cells and smooth muscle cells. One S1P(1) and two S1P(2) siRNA constructs specifically inhibited ectopic expression of S1P(1) and S1P(2) receptors, respectively, as determined by immunocytochemistry and Western blot, and endogenous expression of S1P(1) and S1P(2) receptors in smooth muscle cells, as determined by RT-PCR. Measurement of PLC-beta and Rho kinase activities, which mediate initial and sustained muscle contraction, confirmed receptor silencing and showed that contraction is mediated exclusively by S1P(2) receptors. 相似文献
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The temperate phage P1 encodes two genes whose products antagonize the action of the phage's C1 repressor of lytic functions, namely a distantly linked antirepressor gene, ant, and a closely linked c1 inactivator gene, coi. Starting with an inducible coi-recombinant plasmid, Coi protein was overproduced and purified to near homogeneity. By using a DNA mobility shift assay we demonstrate that Coi protein inhibits the operator binding of the C1 repressors of the closely related P1 and P7 phages. Coi protein (Mr = 7,600) exerts its C1-inactivating function by forming a complex with the C1 repressor (Mr = 32,500) at a molar ratio of about 1:1, as shown by density gradient centrifugation and gel filtration. C1 repressor and Coi protein are recovered in active form from the complex, suggesting that noncovalent interactions are the sole requirements for complex formation. The interplay of repressor and antagonists operating in the life cycle of P1 is discussed. 相似文献