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排序方式: 共有2221条查询结果,搜索用时 15 毫秒
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84.
Nakano M Imamura H Toei M Tamakoshi M Yoshida M Yokoyama K 《The Journal of biological chemistry》2008,283(30):20789-20796
Vacuolar-type H(+)-ATPase (V-ATPase) catalyzes ATP synthesis and hydrolysis coupled with proton translocation across membranes via a rotary motor mechanism. Here we report biochemical and biophysical catalytic properties of V-ATPase from Thermus thermophilus. ATP hydrolysis of V-ATPase was severely inhibited by entrapment of Mg-ADP in the catalytic site. In contrast, the enzyme was very active for ATP synthesis (approximately 70 s(-1)) with the K(m) values for ADP and phosphate being 4.7 +/- 0.5 and 460 +/- 30 microm, respectively. Single molecule observation showed V-ATPase rotated in a 120 degrees stepwise manner, and analysis of dwelling time allowed the binding rate constant k(on) for ATP to be estimated ( approximately 1.1 x 10(6) m(-1) s(-1)), which was much lower than the k(on) (= V(max)/K(m)) for ADP ( approximately 1.4 x 10(7) m(-1) s(-1)). The slower k(on)(ATP) than k(on)(ADP) and strong Mg-ADP inhibition may contribute to prevent wasteful consumption of ATP under in vivo conditions when the proton motive force collapses. 相似文献
85.
Ohi K Hashimoto R Yasuda Y Nemoto K Ohnishi T Fukumoto M Yamamori H Umeda-Yano S Okada T Iwase M Kazui H Takeda M 《PloS one》2012,7(1):e29780
Background
The rs12807809 single-nucleotide polymorphism in NRGN is a genetic risk variant with genome-wide significance for schizophrenia. The frequency of the T allele of rs12807809 is higher in individuals with schizophrenia than in those without the disorder. Reduced immunoreactivity of NRGN, which is expressed exclusively in the brain, has been observed in Brodmann areas (BA) 9 and 32 of the prefrontal cortex in postmortem brains from patients with schizophrenia compared with those in controls.Methods
Genotype effects of rs12807809 were investigated on gray matter (GM) and white matter (WM) volumes using magnetic resonance imaging (MRI) with a voxel-based morphometry (VBM) technique in a sample of 99 Japanese patients with schizophrenia and 263 healthy controls.Results
Although significant genotype-diagnosis interaction either on GM or WM volume was not observed, there was a trend of genotype-diagnosis interaction on GM volume in the left anterior cingulate cortex (ACC). Thus, the effects of NRGN genotype on GM volume of patients with schizophrenia and healthy controls were separately investigated. In patients with schizophrenia, carriers of the risk T allele had a smaller GM volume in the left ACC (BA32) than did carriers of the non-risk C allele. Significant genotype effect on other regions of the GM or WM was not observed for either the patients or controls.Conclusions
Our findings suggest that the genome-wide associated genetic risk variant in the NRGN gene may be related to a small GM volume in the ACC in the left hemisphere in patients with schizophrenia. 相似文献86.
Saitoh Y Mizuno H Xiao L Hyoudou S Kokubo K Miwa N 《Molecular and cellular biochemistry》2012,366(1-2):191-200
Reactive oxygen species has been suggested to be one of the key factors associated with the development of obesity. During spontaneous differentiation of mouse stromal preadipocytes OP9 into adipocytes, intracellular superoxide anion radicals (O (2) (-.) ) level markedly increases and is accompanied by a significant elevation of intracellular lipid accumulation. This differentiation-dependent increase in intracellular O (2) (-.) level positively correlated with the intracellular augmentation of the lipid level. Super-highly hydroxylated fullerene (SHH-F; C(60)(OH)(44)), a novel polyhydroxylated fullerene derivative, quenched intracellular O (2) (-.) , and lipid accumulation to 38.7 and 42.7 % of that in the control, respectively. By thin-layer chromatographic analysis of extracted cellular lipid components, SHH-F clearly decreased the triglycerides ratio in the whole lipid droplet fraction, but scarcely influenced other lipids components. PPARγ2 expression, which plays a key role in regulating adipogenic differentiation, was significantly suppressed by SHH-F at the late stage of differentiation, with unaltered PPARγ1 expression. The intracellular superoxide anion radical augmentation preceded expression of PPARγ2, strongly suggesting that the primary O (2) (-.) generation was closely associated with lipid accumulation and subsequent PPARγ2 induction. These results indicate that SHH-F suppresses intracellular lipid accumulation, particularly in lipid droplets, and decreases O (2) (-.) level and subsequent PPARγ2 upregulation during spontaneous differentiation of OP9 preadipocytes into adipocytes. 相似文献
87.
Iwata H Nakagawa T Yoshioka Y Kagei K Imada K Nakane C Fujita H Suzuki F Nakamura Y 《Bioscience, biotechnology, and biochemistry》2008,72(1):179-185
The pH dependence and kinetics parameters of renin-angiotensinogen reactions were determined using wild-type and S84G mutant human renins and wild-type and H13Y mutant sheep angiotensinogens. It is explained in this report that (i) renin catalyzes acidic and basic reactions of which the optimum pHs are 5.5 and 7.5-8.2 respectively, both of which produce angiotensin I; (ii) Ser84 specific to human renin accelerates the acidic reaction by 75-110% through elevation of V(max), and shifts the optimum pH of the basic reaction from 7.5 to 8.0-8.2; and (iii) His13 specific to sheep angiotensinogen accelerates the acidic and basic reactions by 25-42% through reduction of K(m). It is concluded from these results that the coexistence of Ser84 in renin and His13 in angiotensinogen brings a pH profile of two separate peaks at pHs 5.5 and 8.2 to the reaction of human renin and sheep angiotensinogen. 相似文献
88.
89.
Osaki Y Shirabe T Nakanishi H Wakagi T Yoshimura E 《Metallomics : integrated biometal science》2009,1(4):353-358
Phytochelatins (PCs), non-protein peptides with the general structure [(γ-Glu-Cys)n-Gly (n≥ 2)], are involved in the detoxification of toxic heavy metals mainly in higher plants. The synthesis of the peptides is mediated by phytochelatin synthase (PCS), which is activated by a range of heavy metals. CmPCS, a PCS-like gene found in the genomic DNA of the primitive red alga Cyanidioschyzon merolae, was isolated and a recombinant protein (rCmPCS) fused with a hexahistidine tag at the N-terminus of CmPCS was produced. The finding that this protein mediated PC synthesis from glutathione in a metal-dependent way clearly establishes that rCmPCS is functional. The maximum activity was attained at a reaction temperature of 50 °C, considerably higher than the temperature required for the maximal activity of PCS isolated from the higher plant Silene cucubalus, probably due to the alga being a thermophile. CmPCS showed optimal pH in a slightly higher region than higher plant PCSs, probably due to the less effective charge relay network in the catalytic triad. In addition, the pattern of enzyme activation by metal ions was specific to rCmPCS, with Ag+, Cu2+, and Hg2+ showing only limited activation. In contrast to other eukaryotic PCSs, CmPCS has an extra domain in the N-terminal region from residues 1 to 109, and contains fewer cysteine residues in the C-terminal domain. These differences may be responsible for the metal specificity of the activation of CmPCS. Although the enzyme preparation lost PCS activity progressively when stored at 4 °C, the inclusion of Cd2+ in the preparation effectively prevented the reduction of activity. Furthermore, Cd2+ effectively restored the activity of the inactivated enzyme. These results indicate that Cd2+ ions bind the enzyme to maintain the structural integrity of the peptides. 相似文献
90.
Furuhata S Ando K Oki M Aoki K Ohnishi S Aoyagi K Sasaki H Sakamoto H Yoshida T Ohnami S 《Molecular and cellular biochemistry》2007,298(1-2):125-138
Among the many tissue stem or progenitor cells recently being unveiled, endothelial progenitor cells (EPCs) have attracted
particular attention, not only because of their cardinal role in vascular biology and embryology but also because of their
potential use in the therapeutic development of a variety of postnatal diseases, including cardiovascular and peripheral vascular
disorders and cancer. The aim of this study is to provide some basic and comprehensive information on gene expression of EPCs
to characterize the cells in molecular terms. Here, we focus on EPCs derived from CD34-positive mononuclear cells of human
umbilical cord blood. The EPCs were purified and expanded in culture and analyzed by a high-density oligonucleotide microarray
and real-time RT-PCR analysis. We identified 169 up-regulated and 107 down-regulated genes in the EPCs compared with three
differentiated endothelial cells of human umbilical vein endothelial cells (HUVEC), human lung microvascular endothelial cells
(LMEC) and human aortic endothelial cells (AoEC). It is expected that the obtained list include key genes which are critical
for EPC function and survival and thus potential targets of EPC recognition in vivo and therapeutic modulation of vasculogenesis
in cancer as well as other diseases, in which de novo vasculogenesis plays a crucial role. For instance, the list includes
Syk and galectin-3, which encode protein tyrosine kinase and β-galactoside-binding protein, respectively, and are expressed higher in EPCs than
the three control endothelial cells. In situ hybridization showed that the genes were expressed in isolated cells in the fetal
liver at E11.5 and E14.5 of mouse development. 相似文献