Post-translational S-Nitrosylation Is an Endogenous Factor Fine Tuning the Properties of Human S100A1 Protein

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.     

Effect of neurotropic substances on sleep disorders caused by electrical stimulation of the hypothalamus in cats

The total period of sleep decreased as a result of the REM-sleep deficite following rage reaction induced in cats by the electrical stimulation of the hypothalamus. Haloperidol (1, 2, 3 mg/kg), diazepam (0.5, 1 mg/kg), nitrazepam (1, 6 mg/kg), glutetymide (10, 30, 60 mg/kg), pentobarbital (5, 15, 30 mg/kg) failed to eliminate sleep disturbances induced by rage reaction; lithium hydroxybutyrate (100, 150 mg/kg), dimedrol (1.5, 6 mg/kg) and imipramine increased the total sleep time on account of the slow wave phase; sodium hydroxybutyrate (100 mg/kg) normalized the electrophysiological pattern of sleep, decreasing the REM-sleep latency and the number of waking cats, and increasing the total REM-sleep time and the number of REM-sleep episodes.     

Distribution of N-([1-14C]-palmitoyl)ethanolamine in rat tissues

N-([1-14C]-palmitoyl)-ethanolamine distribution was studied in the rat tissues. The following sequence of the label inclusion into tissues by the way of decreasing the radio activity: adrenal > diaphragm > spleen > kidney > testis > lung > liver > heart > brain > plasma > erythrocytes was obtained.     

Factors improving the accuracy of determination of 15N relaxation parameters in proteins

A number of factors at all stages of data processing which affect the accuracy of determination of 15N relaxation parameters in 15N-labeled proteins is discussed. Methods which allow to improve accuracy of the determined parameters are presented using data obtained for Cucurbita maxima trypsin inhibitor.     

Regularities in the variability of species structure of costal littoral kelp: the model analysis

The model describes species structure of competitive community, inhabiting stochastically variable environment. Species list of this community, rearranged accordingly decreasing species abundance, can be described by decreasing geometrical series. According to the model, the value of coefficient of this progression q should be q = exp(-1) = 0.368. The actual data do not contradict statistically to this model constant. Seasonal variability of species structure in biotopes is observed. These biotopes differ one from another by the stability and heterogeneity levels of environmental conditions, estimated with the help of expert evaluation. Total community biomass shows two seasonal peaks; at winter and at spring - summer. Maximal values of total biomass are observed in the biotope with intermediate level of environment stability. The number of species is increased simultaneously with the growth of environmental stability. The level of species abundance equitability grows up too in these conditions. The model of geometric series describes the species structure of the macroalgae community quite adequately. At the same time, the positive correlation between sample's species richness and equitability of species structure results in the outcome that after all samples averaging the biomass distribution of species is approximately more accurately not by geometrical series but by power model. The new statistical method is offered in the application to this work. It allows the expose of statistically significant not monotone essential non-linear relations of nonquantitative (order-type) arguments.     

Multiple quadrature detection in reduced dimensionality experiments

A new, simple procedure is proposed which enables acquisition of two or more chemical shifts encoded in a common dimension simultaneously in quadrature. For n chemical shifts projected in a single dimension, the expected effect is obtained by interleaved acquisition and appropriate combination of 2ⁿ data sets per increment of respective evolution time. The particular chemical shifts can be calculated from sums and differences of signal frequencies obtained by different combination of the acquired data sets. In comparison to the established reduced dimensionality (RD) techniques, the proposed method enhances resolution due to reduction of the number of signals and requires less evolution time increments owing to narrower spectral width in the RD-domain. We show examples of the application of the new approach to the 2D HNCA and HN(CO)CA techniques with two, and 2D HACANH with three frequencies simultaneously encoded in the t ₁ evolution period, for ¹³C,¹⁵N-labeled ubiquitin.     

Effect of Escapable and Inescapable Stress on Levels of Catecholamines in Adrenals and Corticosterone in Blood Plasma in Young and Aged Rats

Effect of escapable and inescapable electrical stress (ES, IS) on the catecholaminergic system was studied in young (3 months) and aged (25 months) male Wistar rats on the day 3 after stress, using radioimmune analysis and high-pressure liquid chromatography. Catecholamine concentration in adrenals and corticosterone level in blood of control aged rats was lower than in young animals. On the third day after the electrical stimulation in cages with current-conducting floor, production of hormones of adrenal cortical and medullar layers rose significantly in aged rats, with a more pronounced increase of noradrenaline after IS, while of blood adrenaline and corticosterone, after ES. In young rats no significant changes in catecholamines were revealed, whereas the blood corticosterone level was increased after IS. Thus, in aged rats, a low basal level of catecholamines and corticosterone and a delayed stress response can be established. In old animals after ES, a long post-action was observed, which was quite comparable with the results obtained after IS in the both age groups.