Regulation of Phospholipase D Activity by Light and Phytohormones in Oat Seedlings

The effect of synthetic analogs of phytohormones and red light absorbed by phytochrome on the phospholipase D activity (PLD) was studied in oat (Avena sativa L.) seedlings. ABA manifested a short-term stimulating effect on PLD activity in the green seedlings and inhibited phospholipase activity in the etiolated plants. Kinetin inhibited enzyme activity in the etiolated seedlings and did not affect its activity in light. GA did not markedly affect PLD activity in the etiolated plants and activated this enzyme in the green seedlings. Finally, IAA did not affect the enzyme activity. The relationship of the regulatory effects of phytohormones and light on PLD activity is discussed.     

Cloning of the doding cDNA sequence of the gene for Csk tyrosine kinase from human lymphocytes

Tyrosine kinases of the Csk family play an important role in cell growth regulation and normal cell differentiation. They are also involved in carcinogenesis as oncoproteins. The main function of these tyrosine kinases is phosphorylation of tyrosine kinases of the Src family at their C-terminal regions to negatively regulate their activity. Disturbance of csk expression increases the Src tyrosine kinase activity. The full-length coding sequence of the csk cDNA was cloned from human lymphocytes. The 1624-bp cDNA consists of 12 exons and encodes a protein that has conserved SH2 and SH3 domains and is similar to human Csk tyrosine kinase by 99%. The full-length cDNA can be used to analyze the csk structure in normal or illdefined human cells.     

A Mathematical Approach that Includes the Fourier Transform (Plane Wave Decomposition Using Spherical Coordinates) and Simultaneously Assesses Complex Movements,Such as Rotations and Displacements,in Complicated Molecular Constructions

Biophysics - A multimodal mathematical approach is proposed that makes it possible to consider the Fourier objects that arise when macromolecules are described in spherical coordinates. With...     

The structural transitions of erythrocyte membranes induced by cyclic AMP.

The generalized structural transitions of erythrocyte membranes induced by cyclic AMP were registered by ESR, fluorescence, freeze-fracture and circular dichroism methods. Two transitions different in nature were revealed. One, which arises at 10-(11)--10-(10) M cyclic AMP, is cooperative and may be considered as a consequence of interaction of cyclic AMP with a receptor. It was calculated that a structural rearrangement in one erythrocyte ghost is induced by three cyclic AMP molecules. As a result of it the membranes are "loosened". The other transition arises at 10-(10)--10-(8) M cyclic AMP and depends on the activity of the protein kinase system. This transition was shown to be non-cooperative and due to phosphorylation of membranous proteins. During this rearrangement the membranes are "stiffened". Both transitions were demonstrated to relate to the membrane integrity.     

Isolation and Identification of Tyrosine Kinase from the Cytosol of Bovine Retinal Rod Outer Segments

It was shown that the cytosol fraction of bovine retinal rod outer segments contains three forms of tyrosine kinase. One of them was purified 171-fold to attain a specific activity of 1.6 nmol/min per mg protein. The isolated protein had a molecular weight of about 54,000 in SDS electrophoresis. It was shown that this protein is a tyrosine-specific protein kinase, capable of autophosphorylation at the tyrosine residues and restoration of kinase activity upon denaturation–renaturation.     

Protective role of nitric oxide during hydrogen peroxide-induced oxidative stress in tobacco plants

Nitric oxide, produced from exogenous NO donor, sodium nitroprusside, and hydrogen peroxide exerted antagonistic effects on tobacco leaves at micromolar concentrations but induced synergistic effects at millimolar concentrations. During H₂O₂-induced oxidative stress, low concentrations of NO inhibited lipid peroxidation, counteracted the fragmentation of total DNA, and prevented accumulation of soluble proteins in Nicotiana plumbaginifolia cells. When applied at high concentrations, NO induced the caspase-like activity, promoted degradation of DNA and soluble proteins, and reduced ATP synthesis. The results are consistent with the hypothesis that NO performs a dual role in plants, acting as antioxidant (scavenger of reactive oxygen species) and as a signaling messenger. There are grounds to believe that, irrespective of the mechanism involved, nitric oxide performs a protective role during oxidative stress in tobacco leaves, because even high concentrations of NO exerted no immediate toxic effect but induced the programmed cell death through the activation of caspase-like proteases.     

Cloning and analysis of coding cDNA sequence of human leukocyte Csk tyrosine kinase under normal conditions and in choroidal melanoma

The main function of Csk tyrosine kinases is phosphorylation of the C-terminal part of Src tyrosine kinases as a mechanism of their downregulation. A decrease in the expression of csk gene results in the enhancement of Src tyrosine kinase activity. In this study, cDNA containing the full coding sequence of the human leukocyte Csk tyrosine kinase gene has been cloned. The protein encoded by a 1624-bp cDNA fragment has 99% homology to human Csk tyrosine kinase. A comparative sequence analysis of full-length cDNAs for Csk tyrosine kinase of normal lymphocytes and lymphocytes of patients with choroidal melanoma revealed a nucleotide substitution in exon 10 of the gene, which appears to be of diagnostic significance. It has been shown that the risk of choroidal melanoma correlated with the frequency of this allele.     

Transgenic Tobacco Plants Low in Phytochrome A Content

Tobacco (Nicotiana tabacum) plants were transformed with a construct encoding phytochrome A (PHYA) antisense RNA. The construct inserted into the tobacco genome contained squash PHYA cDNA in an antisense orientation under the cauliflower mosaic virus 35S promoter providing for gene expression in higher plant tissues. Using immunoblot analysis and Z3-B1 antibodies against PHYA, the authors demonstrated that the PHYA content of the transgenic plants was lower than that of the wild-type plants. The studies of PHYA-dependent inhibition of hypocotyl elongation by high-intensity far-red light showed a considerable decrease in light sensitivity of the transgenic hypocotyl characteristic for aphyAmutation.     

The structural transitions of erythrocyte membranes induced by cyclic AMP

The generalized structural transitions of erythrocyte membranes induced by cyclic AMP were registered by ESR, fluorescence, freeze-fracture and circular dichroism methods. Two transitions different in nature wre revealed. One, which arises at10^?11-10^?10 M cyclic AMP, is cooperative and may be considered as a consequence of interaciton of cyclic AMP with a receptor. It was calculated that a structural rearrangement in one erythrocyte ghost is induced by three cyclic AMP molecules. As a result of it the membranes are “loosened”.The other transition arises at 10^?10-10^?8 M cyclic AMP and depends on the activity of the protein kinase system. This transition was shown to be non-cooperative and due to phosphorylation of membranous proteins. During this rearrangement the membranes are “stiffened”.Both transitions were demonstrated to related to the membrane integrity.     

The Conformational Stability/Lability of Peptide Fragments in the Sequence Context of Amino Acids

Biophysics - Criteria for evaluating the conformational stability/lability of peptide fragments referred to fragments of protein structures are formulated. Using the proposed criteria, a...