Evidence for allosteric effects on p53 oligomerization induced by phosphorylation

p53 is a tetrameric protein with a thermodynamically unstable deoxyribonucleic acid (DNA)‐binding domain flanked by intrinsically disordered regulatory domains that control its activity. The unstable and disordered segments of p53 allow high flexibility as it interacts with binding partners and permits a rapid on/off switch to control its function. The p53 tetramer can exist in multiple conformational states, any of which can be stabilized by a particular modification. Here, we apply the allostery model to p53 to ask whether evidence can be found that the “activating” C‐terminal phosphorylation of p53 stabilizes a specific conformation of the protein in the absence of DNA. We take advantage of monoclonal antibodies for p53 that measure indirectly the following conformations: unfolded, folded, and tetrameric. A double antibody capture enzyme linked‐immunosorbent assay was used to observe evidence of conformational changes of human p53 upon phosphorylation by casein kinase 2 in vitro. It was demonstrated that oligomerization and stabilization of p53 wild‐type conformation results in differential exposure of conformational epitopes PAb1620, PAb240, and DO12 that indicates a reduction in the “unfolded” conformation and increases in the folded conformation coincide with increases in its oligomerization state. These data highlight that the oligomeric conformation of p53 can be stabilized by an activating enzyme and further highlight the utility of the allostery model when applied to understanding the regulation of unstable and intrinsically disordered proteins.     

Potential of pure and mixed cultures of Cladosporium cladosporioides and Geotrichum candidum for application in bioremediation and detergent industry

The effect of ethoxylated oleyl–cetyl alcohol (Henkel, “Merima”, Serbia) on the growth and metabolic activity of Cladosporium cladosporioides, Geotrichum candidum and their mixed culture was in the focus of this paper. The cultures were grown in Czapek-Dox liquid nutrient medium with the addition of 0.5% pollutant and without it. The physico-chemical and biochemical changes of pH, the total biomass dry weight, the quantity of free and total organic acids, proteolytic activity and the quality of carbohydrates were evaluated from 4th to 19th day of fungal growth. The pollutant caused an inhibitory effect on biomass dry weight of C. cladosporioides and G. candidum for 10.36% and 4.65% respectively, and stimulatory effect on biomass of mixed culture for 3.80%. The pollutant had influence on the decrease in pH value of the media in the phase of culture growth, and pH changes were correlated with the amount of excreted total organic acids. The highest quantity of free and total organic acids was noted in media with pollutant of mixed culture and C. cladosporioides, respectively. The alkaline protease activities of C. cladosporioides, G. candidum and mixed culture were enhanced by addition of pollutant for 56.88%, 55.84% and 30.94% respectively. The obtained results indicate the potential of both pure and mixed cultures in mycoremediation environment contaminated by alcohol ethoxylated and detergent industry.     

Chromium Supplementation Reduces Resting Heart Rate in Patients with Metabolic Syndrome and Impaired Glucose Tolerance

Mental health problems are a major public health issue worldwide, and zinc may be associated with psychiatric symptoms, but such associations have not been investigated extensively. This study was conducted to evaluate the relationship between serum zinc levels and mental health problems in Korean adults. We used data from the Korean National Health and Nutrition Examination Survey V-1, a cross-sectional survey of Korean civilians. Data from 1748 subjects were analyzed. Serum zinc levels did not differ significantly according to psychiatric symptoms including sleep duration, stress, depressed mood, suicidal ideation, and whether respondents sought psychiatric consultation. The frequencies and odds ratios of psychiatric symptoms according to serum zinc tertiles were not significantly associated after adjusting for age, smoking, alcohol consumption, physical activity, body mass index, total body fat, and renal function and for daily fat, carbohydrate, and protein intake. Serum zinc levels may not be associated with psychiatric symptoms in Korean adults without psychiatric disorders.     

Regulation of cytokinin content in plant cells

Cytokinin levels in plant cells are dependent on cytokinin biosynthesis and/or uptake from extracellular sources, metabolic interconversions, inactivation and degradation. Cytokinin conversion to compounds differing in polarity seems to be decisive for their entrapment within the cell and intracellular compartmentation, which affects their metabolic stability. Increase in cytokinin levels, resulting either from their uptake or intracellular biosynthesis, may promote further autoinductive accumulation of cytokinins which may function in the induction of cytokinin-initiated physiological processes. Accumulated cytokinins are capable of inducing cytokinin oxidase which consequently decreases cytokinin levels. This seems to be the mechanism of re-establishment and maintenance of cytokinin homeostasis required for further development of physiological events induced by transient cytokinin accumulation. Auxin may influence cytokinin levels by down regulation of cytokinin biosynthesis and/or by promotion of cytokinin degradation. A model of the regulation of cytokinin levels in plant cells based on these phenomena is presented and its physiological role(s) is discussed.     

ENDOGENOUS CYTOKININS IN THREE GENERA OF MICROALGAE FROM THE CHLOROPHYTA1

Nine axenic microalgal (Chlorophyta) strains from three genera (Protococcus, Chlorella, and Scenedesmus) were analyzed for endogenous cytokinins. Cytokinin‐like activity was detected using the excised cucumber cotyledon bioassay. Five strains showed no cytokinin‐like activity and four strains, low cytokinin‐like activity. Ethanolic extracts of the microalgae containing a mixture of deuterium‐labeled standards were purified using a combined DEAE‐Sephadex octadecysilica column and immunoaffinity column based on wide‐range specific mon‐oclonal antibodies and analyzed by HPLC linked to a micromass single quadrupole mass spectrometer with an electrospray interface and a photodiode array detector. There were similar trends in cytokinin profiles for the nine microalgal strains investigated, although concentrations did vary. Both isopentenyladenine and isopentenyladenosine were detected in all nine strains. cis‐Zeatin and cis‐zeatin riboside occurred at higher concentrations than the trans isomers, whereas trans‐zeatin‐O‐glucoside and trans‐zeatin riboside‐O‐glucoside were dominant over the cis isomers. Dihydrozeatin and its conjugates were not detected in any significant amounts. The aromatic benzyladenine always occurred at higher concentrations than benzyladenosine. The topolins were well represented with all three isomers (ortho, meta, and para) being detected, with ortho‐topolin and ortho‐topolin riboside occurring at higher concentrations than the other isomers. However, for the O‐glucosides, the meta isomers (meta‐topolin‐O‐glucoside and meta‐topolin riboside‐O‐glucoside) occurred at higher concentrations than the other isomers. No N‐glucosides were detected (isopentenyladenine‐9‐glucoside, zeatin‐9‐glucoside, dihydrozeatin‐9‐glucoside, benzyladenine‐9‐glucoside, ortho‐topolin‐9‐glucoside, and meta‐topolin‐9‐glucoside). Generally, zeatin and topolin conjugates were the dominant forms of isoprenoid and aromatic cytokinins, respectively. There was no distinct trend in the proportions of isoprenoid to aromatic cytokinins.     

Experimental allergic encephalomyelitis: changes in growth and proliferation within the draining lymph node following injection of basic encephalitogenic protein in Freund's complete adjuvant

Changes in wet weight, dry mass, and DNA synthesis of draining lymph nodes from rats injected with encephalitogenic basic protein in Freund's complete adjuvant (FCA) were studied. Lymph nodes of rats injected with encephalitogenic basic protein in FCA show accelerated enlargement from the second up to the fourth day after injection, as compared to lymph nodes of rats injected with FCA alone, or with nonencephalitogenic basic protein in FCA. The greatest difference in lymph node weight was found on the fourth day. At this time cell division is higher in the group injected with encephalitogenic protein in FCA than in the group injected with FCA alone. However, the increased division of cells in situ cannot account, in and by itself, for the enlargement of the lymph node which was observed. It is concluded that migration of lymphocytes into the lymph node makes a substantial contribution to the hyperplasia of the lymph node.The results suggest that accelerated lymph node enlargement may be specific, at least in part, for induction of experimental allergic encephalomyelitis.     

Vegetation shift after a clear-cut of non-native dwarf pine (<Emphasis Type="Italic">Pinus mugo</Emphasis>)

Dwarf pine (Pinus mugo) is a shrubby, polycormon-forming woody light-demanding species in the Central-European mountains, but it is non-native in the Jeseniky Mts. (the Hercynian Mts., the Czech Republic). Dwarf pine was introduced there at the nineteenth century, and its range expansion was the reason for the removal of this species by a small-scale clear-cut (locality Keprnik Mt.). The effect of the clear-cutting was recorded by means of phytosociological relevés, and three distinct habitats (alpine grasslands, dwarf pine plantation, clear-cut) were compared 6 years after the dwarf pine removal. On the clear-cut area, the highest species diversity was documented, invasive species were missing there, but plant composition remained transitional and expansive graminoids prevailed. Vegetation shifts denoted environmental changes that were attributed to post-management processes and particular plant attributes. That should be taken into account when planning future large-scale management.     

Binding of transition metals to monosilicic acid in aqueous and xylem (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) solutions: a low-T electron paramagnetic resonance study

The supplementation of monosilicic acid [Si(OH)₄] to the root growing medium is known to protect plants from toxic levels of iron (Fe), copper (Cu) and manganese (Mn), but also to mitigate deficiency of Fe and Mn. However, the physicochemical bases of these alleviating mechanisms are not fully understood. Here we applied low-T electron paramagnetic resonance (EPR) spectroscopy to examine the formation of complexes of Si(OH)₄ with Mn²⁺, Fe³⁺, and Cu²⁺ in water and in xylem sap of cucumber (Cucumis sativus L.) grown without or with supply of Si(OH)₄. EPR, which is also useful in establishing the redox state of these metals, was combined with measurements of total concentrations of metals in xylem sap by inductive coupled plasma. Our results show that Si(OH)₄ forms coordination bonds with all three metals. The strongest interactions of Si(OH)₄ appear to be with Cu²⁺ (1/1 stoichiometry) which might lead to Cu precipitation. In line with this in vitro findings, Si(OH)₄ supply to cucumber resulted in dramatically lower concentration of this metal in the xylem sap. Further, it was demonstrated that Si(OH)₄ supplementation causes pro-reductive changes that contribute to the maintenance of Fe and, in particular, Mn in the xylem sap in bioavailable 2+ form. Our results shed more light on the intertwined reactions between Si(OH)₄ and transition metals in plant fluids (e.g. xylem sap).