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961.
962.
963.
Ferredoxin-NAD(P)(+) reductase [EC 1.18.1.3, 1.18.1.2] was isolated from the green sulfur bacterium Chlorobium tepidum and purified to homogeneity. The molecular mass of the subunit is 42 kDa, as deduced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular mass of the native enzyme is approximately 90 kDa, estimated by gel-permeation chromatography, and is thus a homodimer. The enzyme contains one FAD per subunit and has absorption maxima at about 272, 385, and 466 nm. In the presence of ferredoxin (Fd) and reaction center (RC) complex from C. tepidum, it efficiently catalyzes photoreduction of both NADP(+) and NAD(+). When concentrations of NADP(+) exceeded 10 microM, NADP(+) photoreduction rates decreased with increased concentration. The inhibition by high concentrations of substrate was not observed with NAD(+). It also reduces 2,6-dichlorophenol-indophenol (DPIP) and molecular oxygen with either NADPH or NADH as efficient electron donors. It showed NADPH diaphorase activity about two times higher than NADH diaphorase activity in DPIP reduction assays at NAD(P)H concentrations less than 0.1 mM. At 0.5 mM NAD(P)H, the two activities were about the same, and at 1 mM, the former activity was slightly lower than the latter. 相似文献
964.
Hwang YS Seo JJ Cha SW Lee HS Lee SY Roh DH Kung Hf HF Kim J Ja Park M 《Biochemical and biophysical research communications》2002,292(4):1081-1086
965.
Watanabe T Nakagawa K Ohata S Kitagawa D Nishitai G Seo J Tanemura S Shimizu N Kishimoto H Wada T Aoki J Arai H Iwatsubo T Mochita M Watanabe T Satake M Ito Y Matsuyama T Mak TW Penninger JM Nishina H Katada T 《Developmental biology》2002,250(2):332-347
Mice lacking the stress-signaling kinase SEK1 die from embryonic day 10.5 (E10.5) to E12.5. Although a defect in liver formation is accompanied with the embryonic lethality of sek1(-/-) mice, the mechanism of the liver defect has remained unknown. In the present study, we first produced a monoclonal antibody specifically recognizing murine hepatoblasts for the analysis of liver development and further investigated genetic interaction ofsek1 with tumor necrosis factor-alpha receptor 1 gene (tnfr1) and protooncogene c-jun, which are also responsible for liver formation and cell apoptosis. The defective liver formation in sek1(-/-) embryos was not protected by additionaltnfr1 mutation, which rescues the embryonic lethality of mice lacking NF-kappaB signaling components. There was a progressive increase in the hepatoblast cell numbers of wild-type embryos from E10.5 to E12.5. Instead, impaired hepatoblast proliferation was observed in sek1(-/-) livers from E10.5, though fetal liver-specific gene expression was normal. The impaired phenotype in sek1(-/-) livers was more severe than in c-jun(-/-) embryos, and sek1(-/-) c-jun(-/-) embryos died more rapidly before E8.5. The hepatoblast proliferation required no hematopoiesis, since liver development was not impaired in AML1(-/-) mice that lack hematopoietic functions. Stimulation of stress-activated protein kinase/c-Jun N-terminal kinase by hepatocyte growth factor was attenuated in sek1(-/-) livers. Thus, SEK1 appears to play a crucial role in hepatoblast proliferation and survival in a manner apparently different from NF-kappaB or c-Jun. 相似文献
966.
The native form of serpins (serine protease inhibitors) is metastable, which is critical to their biological functions. Spontaneous conversion from the native form of serpins into a more stable conformation, called the "latent" form, is restricted. To examine whether the connectivity of strand 1 of beta-sheet C to the hydrophobic core is critical to the serpin's preferential folding to the metastable native conformation, we designed a circularly-permuted mutant of alpha(1)-antitrypsin, the prototype serpin, in which strand 1C is disconnected from the hydrophobic core. Conformation of the circular permutant was similar to that of the latent form, as revealed by equilibrium unfolding, limited proteolysis, and spectroscopic properties. Our results support the notion that rapid folding of the hydrophobic core with concomitant incorporation of strand 1C into beta-sheet C traps the serpin molecule into its native metastable conformation. 相似文献
967.
A potent inhibitor of inducible nitric oxide synthase, ONO-1714, a cyclic amidine derivative 总被引:6,自引:0,他引:6
Naka M Nanbu T Kobayashi K Kamanaka Y Komeno M Yanase R Fukutomi T Fujimura S Seo HG Fujiwara N Ohuchida S Suzuki K Kondo K Taniguchi N 《Biochemical and biophysical research communications》2000,270(2):663-667
(1S,5S,6R,7R)-7-Chloro-3-imino-5-methyl-2-azabicyclo[4.1.0]heptane hydrochloride (ONO-1714), a novel cyclic amidine analogue, inhibits human inducible nitric oxide (iNOS) with a K(i) of 1.88 nM and rodent iNOS with similar potency in vitro. ONO-1714 was found to be 10-fold selective for human iNOS over human endothelial NOS (ecNOS). When the inhibitory activity of ONO-1714 was compared for iNOS, it was found to be 451-fold and >20,000-fold more potent than L-NMMA and aminoguanidine (AG), respectively. In terms of human iNOS selectivity, ONO-1714 was approximately 34- and 2-fold more selective for iNOS than L-NMMA and AG, respectively. ONO-1714 inhibited the LPS-induced elevation of plasma nitrate/nitrite in mice with an ID(50) value of 0.010 mg/kg, s.c. The maximum tolerated dose of ONO-1714 was 30 mg/kg, i.v. Thus, ONO-1714 represents one of the most potent iNOS inhibitors in vitro and in vivo to date and has great potentials for use as an inhibitor for clarifying the pathophysiological roles of iNOS and for use as a therapeutic agent. 相似文献
968.
R67 dihydrofolate reductase (DHFR) is an R-plasmid-encoded enzyme that confers clinical resistance to the antibacterial drug trimethoprim. This enzyme shows no sequence or structural homology to the chromosomal DHFRs. The active form of the protein is a homotetramer possessing D(2) symmetry and a single active-site pore. Two tryptophans occur per monomer: W38 and its symmetry-related residues (W138, W238, and W338) occur at the dimer-dimer interfaces, while W45 and its symmetry-related partners (W145, W245, and W345) occur at the monomer-monomer interfaces. Two single-tryptophan mutant genes were constructed to determine the structural and functional consequences of four mutations per tetramer. The W45F mutant retains full enzyme activity and the fluorescence environment of the unmutated W38 residues clearly monitors ligand binding and a pH dependent tetramer right harpoon over left harpoon 2 dimers equilibrium. In contrast, four simultaneous W38F mutations at the dimer-dimer interfaces result in tetramer destabilization. The ensuing dimer is relatively inactive, as is dimeric wild-type R67 DHFR. A comparison of emission spectra indicates the fluorescent signal of wild-type R67 DHFR is dominated by the contribution from W38. Equilibrium unfolding/folding curves at pH 5.0, where all protein variants are dimeric, indicate the environment monitored by the W38 residue is slightly less stable than the environment monitored by the W45 residue. 相似文献
969.
Woo Hong Joo Yong Seung Shin Yeon Lee Sun Mee Park Yong Kee Jeong Jeoung Yoon Seo Jeong Uck Park 《Biotechnology letters》2000,22(12):1021-1024
Pseudomonas sp. BCNU 171, when grown with 10% (v/v) toluene for 2 h, accumulated approximately 7.7 mM trehalose probably arising by the action of trehalose-6-phosphate synthase (E.C. 2.4.1.15). Trehalose may thus play a significant role in the tolerance of the Pseudomonas sp. to toluene. 相似文献
970.
Geum-Sook Do Bong-Bo Seo Jae-Hong Pak In-Sun Kim Seung-Dal Song 《Journal of Plant Biology》2000,43(3):143-148
Using the fluorescence in situ hybridization (FISH) technique, we conducted karyotype analyses to identify the lost chromosomes
in three somaclonal variants obtained from tissue culture of wildAllium tuberosum (2n = 4X = 32). The three lost chromosomes of the At29 variant (2n = 29) were all chromosome 2, the two for At30 (2n = 30)
were chromosomes 7 and 8, and At31 was missing chromosome 2. Chromosome compositions of these variants were confirmed as being
fixed lines during two years of greenhouse cultivation. The bicolor FISH technique, involving both 5S and 18S–5.8S–26S ribosomal
RNA genes as probes, was used to assign chromosomal locations and to confirm whether the lost chromosomes contained any rRNA
markers. The 5S rRNA gene signals in all variants as well as the wild type were detected as two sets, one on the intercalary
region of the short arm of chromosome 3, the other on the intercalary region of the long arm of chromosome 6. One 18S–5.8S–26S
rRNA gene site on the secondary constriction included a flanking satellite and terminal region on the short arm of chromosome
8. Signals of the 18S–5.8S–26S rRNA gene in At30 showpd in only three chromosomes, indicating that one of the lost chromosomes
was chromosome 8. Overall, three marker chromosomes were established by FISH, using rRNA multigene families. 相似文献