Relaxation phenomena in systems of protein-containing reverse micelles of surfactants in organic solvents

The research was aimed to establish the equilibrium processes in protein-containing systems of AOT reverse micelles in octane. As chromophore label for tracing the kinetics of the process, the acid-base indicator, p-nitrophenol, was used. The establishing of the equilibrium in the reverse micelle system notably decelerated in the presence of a solubilized protein (native and stearoylated alpha-chymotrypsin). During the establishing of the equilibrium, the solubilized enzyme can be irreversibly inactivated. The level of the residual activity of the enzyme in the equilibrium system depended on the procedure of micellar system preparation. The methods have been offered to set up the equilibrium in the reverse micelle system without inactivation of the solubilized enzyme.     

The principal difference in regulation of the catalytic activity of water-soluble and membrane forms of enzymes in reversed micelles. Gamma-glutamyltransferase and aminopeptidase

The regularities of their functioning of enzyme, water-soluble and membrane forms, in the systems of the reversed micelles of surfactants in organic solvents are compared. Using as examples gamma-glutamyltransferase (in AOT reversed micelles in octane) and aminopeptidase (in Brij 96 reversed micelles in cyclohexane), the principal difference in the catalytic activity regulation of water-soluble and membrane forms is demonstrated. The catalytic activity of the membrane form depends considerably on the surfactant concentration at the constant degree of hydration, whereas the activity of the water-soluble form is constant under these conditions. The catalytic activity dependence on the surfactant concentration is regarded as a test for enzyme membrane activity.     

Changes in Gene Expression and DNA Methylation of Evolutionarily Young AluY Repeats during Apoptosis of Human K562 Erythro-Myeloblastic Leukemia Cells

Using a human K562 erythromyeloblastoid cell culture, we demonstrated changes in gene expression of Alu repeats, members of evolutionarily young AluY subfamilies (human mobile SINE elements), and in the DNA methylation level of AluYb8 during camptothecin (CAM)-induced apoptosis. The AluY-RNA level increased about 10 times 24 h and 20 times 48 h after exposure to CAM vs. proliferating cells. Using methylation-specific (MSP) PCR and high-resolution melting (HRM), we showed that the overall AluYb8-DNA methylation level remained intact throughout the apoptotic stages. Using DNA sequencing after bisulfite conversion, we established that at the CpG site, located in the A'-box of the AluYb8 gene promoter, the methylation level decreased significantly during different apoptotic stages. Apparently, it is reduced CpG methylation at the A'-box of the AluYb8 gene promoter, discovered in this work, that is one of the possible factors which account for increased expression of AluY repeats during K562 cell apoptosis. We assume that increased gene expression of evolutionarily young AluY repeats plays an important role in the implementation of the cellular apoptotic pathway.     

Computational grounding of point mutagenesis to enhance the thermostability of human peroxiredoxin 6

In this study an algorithm for increasing the thermostability of the globular human peroxyredoxin 6 antioxidant enzyme is described. A recombinant form of this protein was produced based on the analysis of the amino-acid composition of this enzyme in rats (Rattus rattus). The original concept of increasing the thermostability of small globular proteins using alternative hydrogen bonding of the peripheral acidic and basic amino-acid residues was substantially improved by GPU-accelerated molecular-dynamics simulations.     

Competitive interactions of serum protein fractions during complex formation with polycations

Interaction of gamma-globulin with quaternized poly-4-vinylpyridine in water solutions at pH 7 has been studied. Formation of soluble stable cooperative complexes has been observed in a wide range of component ratios. Protein globules are distributed unevenly between adsorbing polycations. Soluble complexes are rod-like particles assembled from the globules which are stabilized by polycation chains. Complex formation in the system gamma-G + PE is similar to that in the system BSA + PE. Competitive interaction of serum protein fractions was studied at the interacting with polycation. It has been shown that selectivity at binding protein fractions is observed in both artificially prepared systems (BSA + gamma-G, beta1-G + gamma-G, BSA + gamma-G + beta1-G), and in serum and whole blood. In those ratios where uneven distribution of protein molecules is observed the soluble complexes protein-PE are formed by separate distribution of individual proteins at the matrix. Decrease of PE concentration in the systems results in the formation of a soluble complex of mixed composition. When an insoluble complex is formed in the system serum-PE selective sorbtion of beta 2-globulin fractions is observed. The reasons for the selective sorbtion of various protein fractions are described, structural models of the soluble complexes protein-PE are suggested.     

Comparative study of the regulation of catalytic activity of soluble and membrane forms of enzymes in reverse micellar systems. Gamma-glutamyltransferase and aminopeptidase]

The regulations of functioning of water soluble and membrane forms of enzymes in the systems of reversed micelles of surfactants in organic solvents are compared. By an examples of gamma-glutamyltransferase (in AOT reversed micelles in octane) and amino-peptidase (in Brij 96 reversed micelles in cyclohexane) the principal difference in the catalytic activity regulation of water soluble and membrane forms is demonstrated. The catalytic activity of the membrane form depends largely on the surfactant concentration at the constant hydration degree, whereas the activity of the water soluble form is constant under these conditions. The catalytic activity dependence on the surfactant concentration is regarded as a "test for the enzyme's membrane activity".     

Fatty acid acylated antibodies against virus suppress its reproduction in cells

A method for suppression of virus reproduction in cells using fatty acylated antiviral antibodies, which in contrast to non-modified antibodies are capable of intracellular penetration, has been suggested. The addition of stearoylated antiviral antibodies to influenza A/Chili virus-infected cells causes a 100-fold suppression of virus reproduction. Non-modified antibodies do not produce any effect on virus reproduction.     

Lipid modification of proteins and their membrane transport

An effective method for artificial attachment of lipid anchors to water-soluble proteins has been developed. To this end, a protein molecule is modified in a system of reversed micelles by a water-insoluble reagent, e.g. fatty acid chloride. Fatty acylated proteins acquire an ability to translocate across lipid membranes and penetrate intact cells. This principle of imparting transmembrane properties to water-soluble proteins makes it possible to realize in vivo a direct transport of antibodies across the hemato-encephalic barrier into the brain and to develop a method for virus suppression by fatty acylated anti-viral antibodies capable of penetrating infected cells. The effect of a drastic increase in the biological activity of exogenous protein factors, e.g. Staphylococcus aureus enterotoxin A, as a result of their artificial fatty acylation has been discovered. The above-mentioned phenomena are discussed in relation to the in vivo data, indicating that post-translational modification of proteins by fatty acids and phospholipids is very widespread in nature and evidently plays an important role in protein transport and sorting. In this connection, lipid modification of proteins is regarded as a possible general step of protein transport in vivo.     

On the possible influence of different pathways of binding of amides with water on “Pyramidalization” of valence bonds of peptide group nitrogen

With the aim to study solvation effects in peptide structure organization, the behavior of the energy of different types of hydration in simple amines and amides has been analyzed. On the example of quantum-chemical DFT and PM3 calculations of amino derivatives of composition CH₃-(CH₂)₃)-NH₂, (CH3)₂-NH, CH₃-NH₂, NH₃, CH₂=CH-NH₂, H-CC-NH₂, O=C(CH)₃-N(CH₃)₂, O=C(CH₃)-NH(CH₃), O=C(CH₃)-NH₂, O=CH-N(CH₃)H, and O=CH-NH₂ it has been shown that: (1) in the given set of molecules, the proton acceptor N…H-O variant of hydrogen bonding of NH₂ group with a water molecule is dominating only for the simplest amines. Being primordially weaker, the proton donor N-H…OH variant of water H-bonding gradually increases in energy in the given set as the basicity of the compound decreases, and for the case of amides of carboxylic acids it becomes already a significant channel of the hydration; (2) the intermolecular N-H…O=C bonding of trans-N-methylacetamides, which models the peptide hydrogen bonds in proteins, induces “planarization” of its initially nonplanar O=C-NH fragments. However, the addition of water molecules to the complex through the proton acceptor N…H-O variant of binding of N atom not only restores but even strengthens the “pyramidalization” of valence bonds of peptide groups.