排序方式: 共有207条查询结果,搜索用时 31 毫秒
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Michael V. LeVine Michel A. Cuendet Asghar M. Razavi George Khelashvili Harel Weinstein 《Biophysical journal》2018,114(1):10-14
Allostery plays a crucial role in the mechanism of neurotransmitter-sodium symporters, such as the human dopamine transporter. To investigate the molecular mechanism that couples the transport-associated inward release of the Na+ ion from the Na2 site to intracellular gating, we applied a combination of the thermodynamic coupling function (TCF) formalism and Markov state model analysis to a 50-μs data set of molecular dynamics trajectories of the human dopamine transporter, in which multiple spontaneous Na+ release events were observed. Our TCF approach reveals a complex landscape of thermodynamic coupling between Na+ release and inward-opening, and identifies diverse, yet well-defined roles for different Na+-coordinating residues. In particular, we identify a prominent role in the allosteric coupling for the Na+-coordinating residue D421, where mutation has previously been associated with neurological disorders. Our results highlight the power of the TCF analysis to elucidate the molecular mechanism of complex allosteric processes in large biomolecular systems. 相似文献
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A novel membrane anchor for FtsZ is linked to cell wall hydrolysis in Caulobacter crescentus 下载免费PDF全文
Elizabeth L. Meier Shiva Razavi Takanari Inoue Erin D. Goley 《Molecular microbiology》2016,101(2):265-280
In most bacteria, the tubulin‐like GTPase FtsZ forms an annulus at midcell (the Z‐ring) which recruits the division machinery and regulates cell wall remodeling. Although both activities require membrane attachment of FtsZ, few membrane anchors have been characterized. FtsA is considered to be the primary membrane tether for FtsZ in bacteria, however in Caulobacter crescentus, FtsA arrives at midcell after stable Z‐ring assembly and early FtsZ‐directed cell wall synthesis. We hypothesized that additional proteins tether FtsZ to the membrane and demonstrate that in C. crescentus, FzlC is one such membrane anchor. FzlC associates with membranes directly in vivo and in vitro and recruits FtsZ to membranes in vitro. As for most known membrane anchors, the C‐terminal peptide of FtsZ is required for its recruitment to membranes by FzlC in vitro and midcell recruitment of FzlC in cells. In vivo, overproduction of FzlC causes cytokinesis defects whereas deletion of fzlC causes synthetic defects with dipM, ftsE and amiC mutants, implicating FzlC in cell wall hydrolysis. Our characterization of FzlC as a novel membrane anchor for FtsZ expands our understanding of FtsZ regulators and establishes a role for membrane‐anchored FtsZ in the regulation of cell wall hydrolysis. 相似文献
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Hasan Jalili Seyed H. Razavi Mohammad Safari F. Xavier Malcata 《Enzyme and microbial technology》2009,45(6-7):469-476
The behavior of Bifidobacterium animalis subsp. lactis Bb 12 under batch cultivation, after continuous culturing for up to 12 d, was monitored in skim milk-based media. Previous continuous culture for longer than 6 d affected the physiology of said microorganism. The minimum inhibitory concentrations of lactic and acetic acids increased from 18 to 26 g/l, whereas the molar ratio of acetic to lactic acid increased from 0.8 to 1.55, when the previous continuous culture increased its duration from 1 to 12 d. The specific lactose consumption rate decreased from 0.94 to 0.77 glactose/gcell dry mass/h within the batch culture timeframe; this was concomitant with greater amounts of acetic and formic acids, and lower amounts of lactic acid produced. The β-galactosidase activity increased as continuous culturing time increased, and reached 446 units/ml by 12 d; however, the rate of enzyme synthesis decreased concomitantly. Succinic acid was produced during the exponential growth and stationary phases of the batch culture, but the former at exponential growth phase was higher as the continuous culturing time was longer. For comparison purposes, batch cultivation of samples taken from continuous cultures by 1 and 12 d was done using a semi-synthetic medium with glucose as carbon source; a pattern similar to that observed when using skim milk-based media was observed. 相似文献
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S. M. Rajaei V. Niknam S. M. Seyedi H. Ebrahimzadeh K. Razavi 《Biologia Plantarum》2009,53(3):523-529
Crocus sativus corms were grown in Perlite and watered by half-strength modified Hoagland nutrient solution containing 0, 50, 100, 150, 200 mM NaCl. Growth parameters
and contents of proteins, proline, polyphenols, minerals and saccharides were studied in fibrous roots, contractile roots,
corms and leaves. All plants remained alive and did not display any sign of foliar damage even at 200 mM NaCl. However, the
salinity decreased growth, relative water content and increased contents of proline and Na+ in all organs. Total protein content was increased in corms and contractile roots but decreased in fibrous roots. Changes
in protein pattern were also observed. Polyphenol content was increased by salinity in all organs except the leaves. As salinity
increased, content of soluble saccharides decreased except in the contractile roots. 相似文献
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The effects of NaCl stress on growth, water status, contents of protein, proline, malondialdehyde (MDA), various sugars and
photosynthetic pigments were investigated in seedlings of Salicornia persica and S. europaea grown in vitro. Seeds were germinated under NaCl (0, 100, 200, 300, 400, 500 and 600 mM) on Murashige and Skoog medium for 45 d. The shoot
growth of both species increased under low NaCl concentration (100 mM) and then decreased with increasing NaCl concentrations.
In contrast to S. persica, root length in S. europaea reduced steadily with an increase in salinity. Proline content in S. persica was higher than in S. europaea at most NaCl concentrations. Proline, reducing saccharide, oligosaccharide and soluble saccharide contents increased under
salinity in both species. In contrast, contents of proteins and polysaccharides reduced in both species under salt stress.
MDA content remained close to control at moderate NaCl concentrations (100 and 200 mM) and increased at higher salinities.
MDA content in S. europaea was significantly higher than S. persica at higher salinities. Salt treatments decreased K+ and P contents in seedlings of both species. Significant reduction in contents of chlorophylls and carotenoids due to NaCl
stress was also observed in seedlings of both species. Some differences appeared between S. persica and S. europaea concerning proteins profile. On the basis of the data obtained, S. persica is more salt-tolerant than S. europaea. 相似文献
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Kheirandish Maryam Siadat Seyed Davar Norouzian Dariush Razavi Mohamad Reza Aghasadeghi Mohammad Reza Rezaei Nima Farazmand Ali Izadi Mobarakeh Jalal Zangeneh Mehrangiz Moshiri Arfa Sadat Seyed Mehdi Salmani Ali Sharifat 《Annals of microbiology》2009,59(4):801-806
Neisseria meningitidis is efficiently phagocytosed by polymorphonuclear leukocytes (PMNS) following opsonization with opsonic antibodies; opsonophagocytosis is the primary mechanism for clearance of meningococci from the host. Thus, in testing meningococcal vaccines, the level of opsonophagocytic antibodies appears to correlate with vaccine-induced protection. Our previous studies demonstrated that the conjugation ofN. meningitidis serogroup A capsular polysaccharide (CPSA) to serogroup B outer membrane vesicle (OMV) could induce a high level of bactericidal antibody response against serogroup A meningococci in animals. The purpose of this study was to evaluate opsonophagocytic activity of the conjugate of CPSA to OMV (CPSA-OMV). In order to evaluate the potential efficacy of CPSA-OMV a flow cytometric opsonophagocytic assay was used. The conjugate and controls were injected intramuscularly into four groups of rabbits with boosters on days 14, 28 and 42 following primary immunization. The rabbits were bled prior to injection and two weeks after each injection. Opsonophagocytic activity of antibodies in hyperimmune sera through rabbit PMNS were measured with flow cytometer, using dihydrorhodamine-123 as a probe. The results indicated that our conjugate could induce a highly significant level of opsonophagocytic activity against serogroup A meningococci after 56 days compared to the control groups (P<0.05). We conclude that this conjugate represents a vaccine candidate against serogroups A and B meningococci after further investigation. 相似文献
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Lee R. Haines Jamie M. Thomas Angela M. Jackson Brett A. Eyford Morteza Razavi Cristalle N. Watson Brent Gowen Robert E. W. Hancock Terry W. Pearson 《PLoS neglected tropical diseases》2009,3(2)