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排序方式: 共有277条查询结果,搜索用时 31 毫秒
141.
Milagros Rocha Celia Ba?uls Lorena Bellod Susana Rovira-Llopis Carlos Morillas Eva Solá Víctor M. Víctor Antonio Hernández-Mijares 《PloS one》2013,8(11)
Retinol binding protein 4 (RBP4) is an adipokine that may contribute to the development of insulin resistance. However, how this adipokine is affected and its possible involvement in lipid metabolism in obese patients with varying degrees of insulin resistance is yet to be determined. A total of 299 middle-aged morbid obese patients (BMI>40 kg/m2) were divided in euglycemic, metabolic syndrome or type 2 diabetic. Anthropometric measurements, biochemical variables and systemic RBP4 levels were determined. RBP4 levels were significantly higher in patients with metabolic syndrome and type 2 diabetes than in euglycemic subjects (42.9±14.6; 42.3±17.0 and 37.4±11.7 µg/ml, respectively) and correlated with triglycerides but not with those of HOMA-IR in the whole population. The multivariate regression model revealed that triglycerides were the strongest predictor of systemic RBP4 levels. Analysis of lipoprotein subfractions in a subpopulation of 80 subjects showed an altered profile of insulin resistant states characterized by higher VLDL, sdLDL and small HDL percentages and lower large HDL percentage. Although RBP4 levels correlated significantly with LDL particle size and small HDL percentage, the latter parameter was independently associated only with RBP4. Our study reveals that systemic RBP4 levels could play an important role in lipid metabolism in morbid obesity, increasing triglyceride levels and contributing to the formation of small HDL. 相似文献
142.
Rosa Milagros Corrales Jade Leiba Martin Cohen-Gonsaud Virginie Molle Laurent Kremer 《Biochemical and biophysical research communications》2013,430(2):858-864
S-Adenosylhomocysteine hydrolase (SahH) is known as an ubiquitous player in methylation-based process that maintains the intracellular S-adenosylhomocysteine (SAH) and S-adenosylmethionine (SAM) equilibrium. Given its crucial role in central metabolism in both eukaryotes and prokaryotes, it is assumed that SahH must be regulated, albeit little is known regarding molecular mechanisms governing its activity. We report here that SahH from Mycobacterium tuberculosis can be phosphorylated by mycobacterial Ser/Thr protein kinases and that phosphorylation negatively affects its enzymatic activity. Mass spectrometric analyses and site-directed mutagenesis identified Thr2 and Thr221 as the two phosphoacceptors. SahH_T2D, SahH_T221D and SahH_T2D/T221D, designed to mimic constitutive phosphorylation, exhibited markedly decreased activity compared to the wild-type enzyme. Both residues are fully conserved in other mycobacterial SahH orthologues, suggesting that SahH phosphorylation on Thr2 and Thr221 may represent a novel and presumably more general mechanism of regulation of the SAH/SAM balance in mycobacteria. 相似文献
143.
Fernando Sánchez-Juanes Laura Ferreira Pablo Alonso de la Vega Angel Valverde Milagros León Barrios Raúl Rivas Pedro F. Mateos Eustoquio Martínez-Molina José Manuel González-Buitrago Martha E. Trujillo Encarna Velázquez 《Systematic and applied microbiology》2013
Genus Bradyrhizobium includes slow growing bacteria able to nodulate different legumes as well as species isolated from plant tumours. The slow growth presented by the members of this genus and the phylogenetic closeness of most of its species difficults their identification. In the present work we applied for the first time Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) to the analysis of Bradyrhizobium species after the extension of MALDI Biotyper 2.0 database with the currently valid species of this genus. With this methodology it was possible to identify strains belonging to phylogenetically closely related species of genus Bradyrhizobium allowing the discrimination among species with rrs gene identities higher than 99%. The application of MALDI-TOF MS to strains isolated from nodules of different Lupinus species in diverse geographical locations allowed their correct identification when comparing with the results of rrs gene and ITS analyses. The nodulation of Lupinus gredensis, an endemic species of the west of Spain, by B. canariense supports the European origin of this species. 相似文献
144.
José M. Bueno Pilar Manzano María C. García Jesús Chicharro Margarita Puente Milagros Lorenzo Adolfo García Santiago Ferrer Rubén M. Gómez María T. Fraile José L. Lavandera José M. Fiandor Jaume Vidal Esperanza Herreros Domingo Gargallo-Viola 《Bioorganic & medicinal chemistry letters》2013,23(24):6938
145.
González-Hernández M Dias PA Romero-Salas D Canales-Espinosa D 《Primates; journal of primatology》2011,52(3):211-216
Group size is related to parasite infections in primates. This relationship probably reflects the fact that group size is
associated with body contact between group members and with contact with contaminated items in the environment. The latter
is highly associated with range use. In the present study we hypothesized that if infection by directly transmitted parasites
(DTP) is mainly determined by the exposure of individuals to parasites that accumulate in the environment, and group size
correlates negatively with the intensity of home range use, then smaller groups should be more infected by DTP. Additionally,
groups that share a higher proportion of their home range with other groups should be more infected. To test our hypothesis
we observed and collected fecal samples of two groups of Alouatta palliata (large group size) and two groups of A. pigra (small group size) that live sympatrically in a forest fragment located in Macuspana (Mexico). Group size was positively
correlated with range area size and negatively correlated with the intensity of home range use. Range use variables were not
related to either DTP prevalence or load. However, there were significant differences in DTP loads between groups, which were
positively correlated with group size. Our results suggest that the intensity of home range use is a poor predictor of DTP
infection parameters in groups with marked differences in size. Therefore, it is possible that the individual or combined
effects of other ecological (e.g., microclimate), social (e.g., contact rate), or physiological (e.g., immune function) factors
are more important in the dynamics of DTP in free-ranging primates. 相似文献
146.
147.
Expression of the chloroplast electron shuttle ferredoxin is induced by light through mechanisms that partially depend on
sequences lying in the coding region of the gene, complicating its manipulation by promoter engineering. Ferredoxin expression
is also down-regulated under virtually all stress situations, and it is unclear if light-dependent induction and stress-dependent
repression proceed through the same or similar mechanisms. Previous reports have shown that expression of a cyanobacterial
flavodoxin in tobacco plastids results in plants with enhanced tolerance to adverse environmental conditions such as drought,
chilling and xenobiotics (Tognetti et al. in Plant Cell 18:2035–2050, 2006). The protective effect of flavodoxin was linked to functional replacement of ferredoxin, suggesting the possibility that
tolerant phenotypes might be obtained by simply increasing ferredoxin contents. To bypass endogenous regulatory constraints,
we transformed tobacco plants with a ferredoxin gene from Anabaena sp. PCC7120, which has only 53% identity with plant orthologs. The cyanobacterial protein was able to interact in vitro with
ferredoxin-dependent plant enzymes and to mediate NADP+ photoreduction by tobacco thylakoids. Expression of Anabaena ferredoxin was constitutive and light-independent. However, homozygous lines accumulating threefold higher ferredoxin levels
than the wild-type failed to show enhanced tolerance to oxidative stress and chilling temperatures. Under these adverse conditions,
Anabaena ferredoxin was down-regulated even faster than the endogenous counterparts. The results indicate that: (1) light- and stress-dependent
regulations of ferredoxin expression proceed through different pathways, and (2) overexpression of ferredoxin is not an alternative
to flavodoxin expression for the development of increased stress tolerance in plants. 相似文献
148.
Hernández-Ortega A Lucas F Ferreira P Medina M Guallar V Martínez AT 《The Journal of biological chemistry》2011,286(47):41105-41114
Aryl-alcohol oxidase (AAO) is a flavoenzyme responsible for activation of O2 to H2O2 in fungal degradation of lignin. The AAO crystal structure shows a buried active site connected to the solvent by a hydrophobic funnel-shaped channel, with Phe-501 and two other aromatic residues forming a narrow bottleneck that prevents the direct access of alcohol substrates. However, ligand diffusion simulations show O2 access to the active site following this channel. Site-directed mutagenesis of Phe-501 yielded a F501A variant with strongly reduced O2 reactivity. However, a variant with increased reactivity, as shown by kinetic constants and steady-state oxidation degree, was obtained by substitution of Phe-501 with tryptophan. The high oxygen catalytic efficiency of F501W, ∼2-fold that of native AAO and ∼120-fold that of F501A, seems related to a higher O2 availability because the turnover number was slightly decreased with respect to the native enzyme. Free diffusion simulations of O2 inside the active-site cavity of AAO (and several in silico Phe-501 variants) yielded >60% O2 population at 3–4 Å from flavin C4a in F501W compared with 44% in AAO and only 14% in F501A. Paradoxically, the O2 reactivity of AAO decreased when the access channel was enlarged and increased when it was constricted by introducing a tryptophan residue. This is because the side chain of Phe-501, contiguous to the catalytic histidine (His-502 in AAO), helps to position O2 at an adequate distance from flavin C4a (and His-502 Nϵ). Phe-501 substitution with a bulkier tryptophan residue resulted in an increase in the O2 reactivity of this flavoenzyme. 相似文献
149.
Aldeco M Arslan BK Edmondson DE 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2011,159(2):78-83
A comparative investigation of substrate specificity and inhibitor binding properties of recombinant zebrafish (Danio rerio) monoamine oxidase (zMAO) with those of recombinant human monoamine oxidases A and B (hMAO A and hMAO B) is presented. zMAO oxidizes the neurotransmitter amines (serotonin, dopamine and tyramine) with k(cat) values that exceed those of hMAO A or of hMAO B. The enzyme is competitively inhibited by hMAO A selective reversible inhibitors with the exception of d-amphetamine where uncompetitive inhibition is exhibited. The enzyme is unreactive with most MAO B-specific reversible inhibitors with the exception of chlorostyrylcaffeine. zMAO catalyzes the oxidation of para-substituted benzylamine analogs exhibiting (D)k(cat) and (D)(k(cat)/K(m)) values ranging from 2 to 8. Structure-activity correlations show a dependence of log k(cat) with the electronic factor σ(p) with a ρ value of +1.55±0.34; a value close to that for hMAO A but not with MAO B. zMAO differs from hMAO A or hMAO B in benzylamine analog binding correlations where an electronic effect (ρ=+1.29±0.31) is observed. These data demonstrate zMAO exhibits functional properties similar to hMAO A as well as exhibits its own unique behavior. These results should be useful for studies of MAO function in zebrafish models of human disease states. 相似文献
150.
Sagasti S Yruela I Bernal M Lujan MA Frago S Medina M Picorel R 《Metallomics : integrated biometal science》2011,3(2):169-175
The goal of the present work was to characterize the recombinant copper chaperone (CCS) from soybean. Very little is known about plant copper chaperones, which makes this study of current interest, and allows for a comparison with the better known homologues from yeast and humans. To obtain sizeable amounts of pure protein suitable for spectroscopic characterization, we cloned and overexpressed the G. max CCS chaperone in E. coli in the presence of 0.5 mM CuSO(4) and 0.5 mM ZnSO(4) in the broth. A pure protein preparation was obtained by using two IMAC steps and pH gradient chromatography. Most of the proteins were obtained as apo-form, devoid of copper atoms. The chaperone showed a high content (i.e., over 40%) of loops, turns and random coil as determined both by circular dichroism and homology modelling. The homology 3-D structural model suggests the protein might fold in three structural protein domains. The 3-D model along with the primary structure and spectroscopic data may suggest that copper atoms occupy the two metal binding sites, MKCEGC and CTC, within the N-terminal domain I and C-terminal domain III, respectively. But only one Zn-binding site was obtained spectroscopically. 相似文献