排序方式: 共有117条查询结果,搜索用时 78 毫秒
21.
Liliya Vugmeyster Tien Do Dmitry Ostrovsky Riqianq Fu 《Protein science : a publication of the Protein Society》2014,23(2):145-156
Thermostable villin headpiece protein (HP67) consists of the N‐terminal subdomain (residues 10–41) and the autonomously folding C‐terminal subdomain (residues 42–76) which pack against each other to form a structure with a unified hydrophobic core. The X‐ray structures of the isolated C‐terminal subdomain (HP36) and its counterpart in HP67 are very similar for the hydrophobic core residues. However, fine rearrangements of the free energy landscape are expected to occur because of the interactions between the two subdomains. We detect and characterize these changes by comparing the µs‐ms time scale dynamics of the methyl‐bearing side chains in isolated HP36 and in HP67. Specifically, we probe three hydrophobic side chains at the interface of the two subdomains (L42, V50, and L75) as well as at two residues far from the interface (L61 and L69). Solid‐state deuteron NMR techniques are combined with computational modeling for the detailed characterization of motional modes in terms of their kinetic and thermodynamic parameters. The effect of interdomain interactions on side chain dynamics is seen for all residues but L75. Thus, changes in dynamics because of subdomain interactions are not confined to the site of perturbation. One of the main results is a two‐ to threefold increase in the value of the activation energies for the rotameric mode of motions in HP67 compared with HP36. Detailed analysis of configurational entropies and heat capacities complement the kinetic view of the degree of the disorder in the folded state. 相似文献
22.
Amandine Renaud de la Faverie Aurore Guédin Amina Bedrat Liliya A. Yatsunyk Jean-Louis Mergny 《Nucleic acids research》2014,42(8):e65
Thioflavin T (ThT) becomes fluorescent in the presence of the G-quadruplex structure such as that formed by the human telomeric motif. In this report, we extend and generalize these observations and show that this dye may be used as a convenient and specific quadruplex probe. In the presence of most, but not all, G4-forming sequences, we observed a large increase in ThT fluorescence emission, whereas the presence of control duplexes and single strands had a more limited effect on emission. This differential behavior allowed us to design a high-throughput assay to detect G4 formation. Hundreds of different oligonucleotides may be tested in parallel for G4 formation with a simple fluorescence plate reader. We applied this technique to a family of aptamers not previously recognized as G4-forming sequences and demonstrated that ThT fluorescence signal may be used to predict G4 formation. 相似文献
23.
The solvent-free condensation of heptafluorobutanal and pyrrole leads to the corresponding meso-alkyl-substituted corrole, which was metallated by gallium chloride to provide the first first-row non-transition-metal corrole. Both the ligand and the complex were characterized by X-ray crystallography. 相似文献
24.
Martina Lenar?i? ?ivkovi? Monika Zar?ba-Kozio? Liliya Zhukova Jaros?aw Poznański Igor Zhukov Aleksandra Wys?ouch-Cieszyńska 《The Journal of biological chemistry》2012,287(48):40457-40470
S100A1 is a member of the Ca2+-binding S100 protein family. It is expressed in brain and heart tissue, where it plays a crucial role as a modulator of Ca2+ homeostasis, energy metabolism, neurotransmitter release, and contractile performance. Biological effects of S100A1 have been attributed to its direct interaction with a variety of target proteins. The (patho)physiological relevance of S100A1 makes it an important molecular target for future therapeutic intervention. S-Nitrosylation is a post-translational modification of proteins, which plays a role in cellular signal transduction under physiological and pathological conditions. In this study, we confirmed that S100A1 protein is endogenously modified by Cys85
S-nitrosylation in PC12 cells, which are a well established model system for studying S100A1 function. We used isothermal calorimetry to show that S-nitrosylation facilitates the formation of Ca2+-loaded S100A1 at physiological ionic strength conditions. To establish the unique influence of the S-nitroso group, our study describes high resolution three-dimensional structures of human apo-S100A1 protein with the Cys85 thiol group in reduced and S-nitrosylated states. Solution structures of the proteins are based on NMR data obtained at physiological ionic strength. Comparative analysis shows that S-nitrosylation fine tunes the overall architecture of S100A1 protein. Although the typical S100 protein intersubunit four-helix bundle is conserved upon S-nitrosylation, the conformation of S100A1 protein is reorganized at the sites most important for target recognition (i.e. the C-terminal helix and the linker connecting two EF-hand domains). In summary, this study discloses cysteine S-nitrosylation as a new factor responsible for increasing functional diversity of S100A1 and helps explain the role of S100A1 as a Ca2+ signal transmitter sensitive to NO/redox equilibrium within cells. 相似文献
25.
The Arabidopsis MAP kinase kinase MKK1 participates in defence responses to the bacterial elicitor flagellin 总被引:6,自引:0,他引:6
Mészáros T Helfer A Hatzimasoura E Magyar Z Serazetdinova L Rios G Bardóczy V Teige M Koncz C Peck S Bögre L 《The Plant journal : for cell and molecular biology》2006,48(4):485-498
Plants sense pathogens through both pathogen-associated molecular patterns and recognition of race-specific virulence factors, which induce basal defence or an accelerated defence (often manifest in the form of local cell death), respectively. A mitogen-activated protein kinase (MAPK) module in Arabidopsis was previously proposed to signal from perception of the bacterial elicitor flagellin to the activation of basal defence-related genes. Here, we present evidence for a parallel MAPK-signalling pathway involved in the response to flg22, a peptide corresponding to the most conserved domain of flagellin. The endogenous Arabidopsis MAP kinase kinase MKK1 is activated in cells treated with flg22, phosphorylates the MAPK MPK4 in vitro, and activates it in vivo in protoplasts. In mkk1 mutant plants, the activation by flg22 of MPK4 and two other flg22-induced MAPKs (MPK3 and MPK6) is impaired. In the mkk1 mutant, a battery of both flg22-induced and flg22-repressed genes show altered expression, indicating that MKK1 negatively regulates the activity of flagellin-responsive genes. Intriguingly, in contrast to the mpk4 mutant, mkk1 shows no morphological anomalies and is compromised in resistance to both virulent and avirulent Pseudomonas syringae strains. Thus, the MKK1 signalling pathway modulates the expression of genes responding to elicitors and plays an important role in pathogen defence. 相似文献
26.
Dematin is an actin-binding protein abundant in red blood cells and other tissues. It contains a villin-type ‘headpiece’ F-actin-binding
domain at its extreme C-terminus. The isolated dematin headpiece domain (DHP) undergoes a significant conformational change
upon phosphorylation. The mutation of Ser74 to Glu closely mimics the phosphorylation of DHP. We investigated motions in the
backbone of DHP and its mutant DHPS74E using several complementary NMR relaxation techniques: laboratory frame 15N NMR relaxation, which is sensitive primarily to the ps–ns time scale, cross-correlated chemical shift modulation NMR relaxation
detecting correlated μs–ms time scale motions of neighboring 13C′ and 15N nuclei, and cross-correlated relaxation of two 15N–1H dipole–dipole interactions detecting slow motions of backbone NH vectors in successive amino acid residues. The results
indicate a reduction in mobility upon the mutation in several regions of the protein. The additional salt bridge formed in
DHPS74E that links the N- and C-terminal subdomains is likely to be responsible for these changes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
27.
Cláudia Pascoal Fernanda Cássio Liliya Nikolcheva Felix Bärlocher 《Microbial ecology》2010,59(1):84-93
Freshwaters include some of the most impaired systems on Earth with high rates of species loss, underscoring the significance
of investigating whether ecosystems with fewer species will be able to maintain ecological processes. The environmental context
is expected to modulate the effects of declining diversity. We conducted microcosm experiments manipulating fungal inoculum
diversity and zinc concentration to test the hypothesis that fungal diversity determines the susceptibility of leaf litter
decomposition to Zn stress. Realized fungal diversity was estimated by counting released spores and by measuring species-specific
biomasses via denaturing gradient gel electrophoresis. In the absence of Zn, positive diversity effects were found for leaf
mass loss and fungal biomass through complementary interactions and due to the presence of key species. The variability of
leaf decomposition decreased with increasing species number (portfolio effect), particularly under Zn stress. Results suggest
that the effect of species loss on ecosystem stability may be exacerbated at higher stress levels. 相似文献
28.
29.
Genetic transformation of barley (Hordeum vulgare L.) via infection of androgenetic pollen cultures with Agrobacterium tumefaciens 总被引:2,自引:0,他引:2
A novel genetic transformation method for barley (Hordeum vulgare L.), based on infection of androgenetic pollen cultures with Agrobacterium tumefaciens, is presented. Winter-type barley cv. 'Igri' was amenable to stable integration of transgenes mediated by A. tumefaciens strain LBA4404 harbouring a vector system that confers hypervirulence, or by the non-hypervirulent strain GV3101 with a standard binary vector. The efficacy of gene transfer was substantially influenced by pollen pre-culture time, choice of Agrobacterium strain and vector system, Agrobacterium population density, medium pH and the concentrations of acetosyringone, CaCl(2) and glutamine. After co-culture, rapid removal of viable agrobacteria was crucial for subsequent development of the pollen culture. To this end, the growth of agrobacteria was suppressed by the concerted effects of appropriate antibiotics, low pH, reduced level of glutamine and high concentrations of CaCl(2) and acetosyringone. Following infection with LBA4404 and GV3101, about 31% and 69%, respectively, of the primary transgenic (T(0)) plants carried a single copy of the sequence integrated. The use of hypervirulent A. tumefaciens and hygromycin resistance as a selectable marker resulted in 3.7 T(0) plants per donor spike. About 60% of the primary transgenic plants set seed, indicating spontaneous genome doubling. An analysis of 20 T(1) populations revealed that four progenies did not segregate for reporter gene expression. This indicates that the approach pursued enables the generation of instantly homozygous primary transgenic plants. The method established will be a valuable tool in functional genomics as well as for the biotechnological improvement of barley. 相似文献
30.
A fascinating group of enzymes has been shown to possess multiple active sites connected by intramolecular tunnels for the passage of reactive intermediates from the site of production to the site of utilization. In most of the examples studied to date, the binding of substrates at one active site enhances the formation of a reaction intermediate at an adjacent active site. The most common intermediate is ammonia, derived from the hydrolysis of glutamine, but molecular tunnels for the passage of indole, carbon monoxide, acetaldehyde and carbamate have also been identified. The architectural features of these molecular tunnels are quite different from one another, suggesting that they evolved independently. 相似文献