The DUSP domain of pseudophosphatase MK-STYX interacts with G3BP1 to decrease stress granules.

Mitogen activated protein kinase phosphoserine/threonine/tyrosine-binding protein (MK-STYX) is a dual specificity (DUSP) member of the protein tyrosine phosphatase family. It is a pseudophosphatase, which lacks the essential amino acids histidine and cysteine in the catalytic active signature motif (HCXR). We previously reported that MK-STYX interacts with G3BP1 [Ras-GAP (GTPase-activating protein) SH3 (Src homology 3) domain-binding-1] and reduces stress granules, stalled mRNA.

Heterodimeric neurotoxic phospholipases A2--the first proteins from venom of recently established species Vipera nikolskii: implication of venom composition in viper systematics.

For the first time the venom of recently established viper species Vipera nikolskii was fractionated and two heterodimeric phospholipases A(2) (HDP-1 and HDP-2) were isolated. Isolation of HDP-1 and HDP-2 is the first indication of the presence of two heterodimeric phospholipases A(2) in the venom of one viper species. When tested on the frog neuromuscular junction, isolated proteins affected neuromuscular transmission acting presynaptically.

[A composite polyaniline-containing silica sorbent for DNA isolation].

A composite sorbent based on porous glass beads modified with thin polyaniline coating was prepared by precipitating aniline polymerization in the presence of carrier particles. It was shown that the modification ensures the uniform coating of the inner surface of the carrier pores with the polymer layer approximately 70 A thick. It was shown that the resulting material retains the initial porosity of the carrier and is selective in the separation of nucleic acids and proteins.

[Composite fluorine polymer-containing sorbents for isolation and purification of biopolymers].

Composite fluoropolymer-containing sorbents based on porous silicas were synthesized for the isolation and purification of biopolymers under nondenaturing conditions. Examples of the application of these sorbents in the separation of various mixtures of peptides and proteins and purification of nucleic acids from various sources (plasmid DNA and DNA from nucleated human blood cells) using the cartridge, column, and batch (sorption in a stirred volume) methods are presented. It was shown that the sorbents can be used in laboratory practice because they are selective to nucleic acids (DNA and RNA) and proteins.

[Dependence of pepsin conformational states on pH and temperature].

A conformational behaviour of pepsin depending on pH and temperature was studied by circular dichroism, differential UV-spectroscopy, calorimetry and enzymatic hydrolysis kinetics. A subtile conformational transition of the enzyme accompanied by changes in the physico-chemical and enzymatic properties of the protein was observed within the temperature interval of 15--40 degrees and within the pH range of 1,1--5,6. The range of pepsin heat denaturation was studied.

[Influence of pH and thermal treatment on the intramolecular mobility of pepsin].

In connection with a hypothesis of segmental flexibility of pepsin and its derivative aminopepsin (containing 3-aminotyrosine residues), a dynamic behaviour of pepsin and dansylated aminopepsin in aqueous solutions at pH 1.0--8.3 in investigated.

[The fluorescence of pepsin conjugates with DNS-chloride].

Parameters of rotational relaxation of pepsin conjugated in neutral and slightly alkaline solutions with a fluorescent label 1-dimethylaminonaphthalene-5-sulphonyl chloride (DNS-Cl) are measured by a fluorescence polarization method. It is shown that the globule of pepsin denatured and loose at lakaline pH values converts into a compact form after transfer to acidic solution. The compactness of this new form is close to that of native inhibited pepsin.

[Intramolecular mobility of pepsin].

By modifying four tyrosine residues in pepsin a derivative (aminopepsin) is obtained which is capable to conjugate with a fluorescent label DNS-Cl without loss of the catalytic activity. Rotational relaxation times of native pepsin and dansylated aminopepsin (DAP) are measured by a fluoresence polarization method. The values obtained are shown to be lower than those calculated for arigid pepsin globule.

[pH-dependence of the mechanism of pepsin action].

N-Acetyl-L-phenylalanine inhibition of the peptic hydrolysis of N-acetyl-L-phenylalanine-L-tyrosine over the pH range 2-4.5 was studied. The mixed character of inhibition which was partially competitive and partially non-competitive allowed us to infer that the separate steps of the enzymatic hydrolysis were pH dependent.