Q15831284
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8., upravené vydání 175 stran ; 21 cm
Příručka pro střední školy, která obsahuje otázky z fyziky, které se zaměřují na přijímací zkoušky na vysokou školu.
- Konspekt
- Fyzika
- Učební osnovy. Vyučovací předměty. Učebnice
- NLK Obory
- fyzika, biofyzika
- NLK Publikační typ
- učebnice středních škol
- testy
- otázky a odpovědi
7., upravené vydání 175 stran ; 21 cm
Soubor testových otázek z fyziky, který je určen pro studenty lékařství i studenty bakalářských i magisterských oborů na 2. lékařské fakultě Univerzity Karlovy.; Soubor modelových otázek a odpovědí je určen zájemcům o magisterské i bakalářské studium na 2. lékařské fakultě Univerzity Karlovy v Praze.
- Konspekt
- Fyzika
- Učební osnovy. Vyučovací předměty. Učebnice
- NLK Obory
- fyzika, biofyzika
- NLK Publikační typ
- testy
6. vyd. 175 s. ; 21 cm
1. vyd. 63 s. ; 21 cm
Yeast 14-3-3 protein isoforms BMH1 and BMH2 possess a distinctly variant C-terminal tail which differentiates them from the isoforms of higher eukaryotes. Their C-termini are longer and contain a polyglutamine stretch of unknown function. It is now well established that the C-terminal segment of 14-3-3 proteins plays an important regulatory role by functioning as an autoinhibitor which occupies the ligand binding groove and blocks the binding of inappropriate ligands. Whether the same holds true or not for the yeast isoforms is unclear. Therefore, we investigated the conformational behavior of the C-terminal segment of BMH proteins using various biophysical techniques. Dynamic light scattering, sedimentation velocity, time-resolved fluorescence anisotropy decay, and size exclusion chromatography measurements showed that the molecules of BMH proteins are significantly larger compared to the human 14-3-3zeta isoform. On the other hand, the sedimentation analysis confirmed that BMH proteins form dimers. Time-resolved tryptophan fluorescence experiments revealed no dramatic structural changes of the C-terminal segment upon the ligand binding. Taken together, the C-terminal segment of BMH proteins adopts a widely opened and extended conformation that makes difficult its folding into the ligand binding groove, thus increasing the apparent molecular size. It seems, therefore, that the C-terminal segment of BMH proteins does not function as an autoinhibitor.
- MeSH
- aminokyselinové motivy MeSH
- dimerizace MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární sekvence - údaje MeSH
- proteiny 14-3-3 chemie genetika metabolismus MeSH
- Saccharomyces cerevisiae - proteiny chemie genetika metabolismus MeSH
- Saccharomyces cerevisiae chemie genetika metabolismus MeSH
- sekvence aminokyselin MeSH
- sekvenční seřazení MeSH
- terciární struktura proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
We characterized physical and chemical properties of cell-membrane fragments from Bacillus subtilis 168 (trpC2) grown at pH 5.0, 7.0 and 8.5. Effects of long-term bacterial adaptation reflected in growth rates and in changes of the membrane lipid composition were correlated with lipid order and dynamics using time-resolved fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene. We demonstrate that the pH adaptation results in a modification of a fatty acid content of cellular membranes that significantly influences both the lipid-chain order and dynamics. For cultivation at acidic conditions, the lipid order increases and membrane dynamics decreases compared to pH 7.0. This results in rigid and ordered membranes. Cultivation at pH 8.5 causes slight membrane disordering. Instant pH changes induce qualitatively similar but smaller effects. Proton flux measurements performed on intact cells adapted to both pH 5.0 and 8.5 revealed lower cell-membrane permeability compared to bacteria cultivated at pH optimum. Our results indicate that both acidic and alkalic pH stress represent a permanent challenge for B. subtilis to keep a functional membrane state. The documented adaptation-induced adjustments of membrane properties could be an important part of mechanisms maintaining an optimal intracellular pH at a wide range of extracellular proton concentrations.
Tyrosine hydroxylase (TH) catalyzes the first step in the biosynthesis of catecholamines. Regulation of TH enzyme activity is controlled through the posttranslational modification of its regulatory domain. The regulatory domain of TH can be phosphorylated at four serines (8, 19, 31, and 40) by a variety of protein kinases. Phosphorylation of Ser19 does not by itself increase TH activity but induces its binding to the 14-3-3 protein. That leads to the enhancement of TH activity with a still not fully understood mechanism. The main goal of this work was to investigate whether the 14-3-3 protein binding affects the conformation of the regulatory domain of human TH isoform 1 (TH1R). Site-directed mutagenesis was used to generate five single-tryptophan mutants of TH1R with the Trp residue located at five different positions within the domain (positions 14, 34, 73, 103, and 131). Time-resolved tryptophan fluorescence measurements revealed that phosphorylation of Ser19 and Ser40 does not itself induce any significant structural changes in regions surrounding inserted tryptophans. On the other hand, the interaction between the 14-3-3 protein and phosphorylated TH1R decreases the solvent exposure of tryptophan residues at positions 14 and 34 and induces distinct structural change in the vicinity of Trp73. The 14-3-3 protein binding also reduces the sensitivity of phosphorylated TH1R to proteolysis by protecting its N-terminal part (first 33 residues). Circular dichroism measurements showed that TH1R is an unstructured protein with a low content of secondary structure and that neither phosphorylation nor the 14-3-3 protein binding changes its secondary structure.
- MeSH
- cirkulární dichroismus MeSH
- elektroforéza v polyakrylamidovém gelu MeSH
- financování organizované MeSH
- fluorescenční spektrometrie MeSH
- fosforylace MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární sekvence - údaje MeSH
- mutageneze cílená MeSH
- proteiny 14-3-3 fyziologie MeSH
- sekvence aminokyselin MeSH
- tyrosin-3-monooxygenasa genetika chemie metabolismus MeSH
- Check Tag
- lidé MeSH
FoxO4 belongs to the "O" subset of forkhead transcription factors, which participate in various cellular processes. The forkhead DNA binding domain (DBD) consists of three-helix bundle resting on a small antiparallel beta-sheet from which two extended loops protrude and create two wing-like structures. The wing W2 of FoxO factors contains a 14-3-3 protein-binding motif that is phosphorylated by protein kinase B in response to insulin or growth factors. In this report, we investigated the role of the N-terminal loop (portion located upstream of first helix H1) and the C-terminal region (loop known as wing W2) of the forkhead domain of transcription factor FoxO4 in DNA binding. Although the deletion of either portion partly reduces the FoxO4-DBD binding to the DNA, the simultaneous deletion of both regions inhibits DNA binding significantly. Förster resonance energy transfer measurements and molecular dynamics simulations suggest that both studied N- and C-terminal regions of FoxO4-DBD directly interact with DNA. In the presence of the N-terminal loop the protein kinase B-induced phosphorylation of wing W2 by itself has negligible effect on DNA binding. On the other hand, in the absence of this loop the phosphorylation of wing W2 significantly inhibits the FoxO4-DBD binding to the DNA. The binding of the 14-3-3 protein efficiently reduces DNA-binding potential of phosphorylated FoxO4-DBD regardless of the presence of the N-terminal loop. Our results show that both N- and C-terminal regions of forkhead domain are important for stability of the FoxO4-DBD.DNA complex
- MeSH
- anizotropie MeSH
- delece genu MeSH
- DNA chemie MeSH
- financování organizované MeSH
- fosforylace MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární modely MeSH
- molekulární sekvence - údaje MeSH
- proteiny 14-3-3 chemie MeSH
- protoonkogenní proteiny c-akt chemie MeSH
- sekundární struktura proteinů MeSH
- sekvence aminokyselin MeSH
- terciární struktura proteinů MeSH
- transkripční faktory chemie metabolismus MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
We investigated the effect of temperature on the binding specificity of the recombinant d-trehalose/d-maltose-binding protein from the hyperthermophilic archaeon Thermococcus litoralis (TMBP). Importantly, we found that TMBP can bind d-glucose (Glc). The Glc binding was characterized by means of fluorescence spectroscopy in the temperature range of 25 degrees C-85 degrees C. Our results show that at 25 degrees C the binding of Glc to TMBP is well represented by a bimodal model with apparent K(d) of 20 muM and approximately 3-8 mM for the first and the second binding step, respectively. At 60 degrees C the binding of Glc to TMBP is represented by a simple hyperbolic model with an apparent K(d) value of about 40 muM. Finally, at 85 degrees C Glc did not bind to TMBP. Molecular dynamics (MD) simulations were used to shed light on the molecular mechanism of the Glc binding. Our results suggest that after proper fluorescent labeling TMBP can be used as a highly thermostable and non-consuming analyte biosensor for monitoring the level of glucose in fluids (e.g. human blood) where other sugars are not present.
