Isolation and characteristics of antibodies against synthetic fragments of oncoproteins. II. Antiserum against the transforming protein pp60src of Rous sarcoma virus

To generate the antibodies to the transforming protein of Rous sarcoma virus (RSV) pp60src, rabbits were immunized with the peptide, corresponding to 415-421 sequence of pp60src. These antibodies immunoprecipitate pp60src in RSV-transformed chicken and mammalian cells, and also some proteins (45, 85 and 120 kDa), which could be autophosphorylated in vitro. It was shown that 415-421 sequence of pp60src is not recognized by the antibodies to pp60src from RSV-induced tumour bearing rabbits (TBR serum). In contrast to TBR serum, antibodies, generated against synthetic peptide, corresponding 415-421 sequence of pp60src couldn't be phosphorylated in vitro, when [gamma-32P]ATP is added to the immune complex. The antipeptide antibodies, bound to pp60src did not block phosphorylation of TBR immunoglobulins, added to this immune complex. Hence, 415-421 sequence of pp60src RSV containing the major tyrosine phosphorylation site does not take part in the kinase reaction in vitro.     

Biochemical bases of prevention of the cytotoxic effect of xenobiotics]

Possible sources of cytotoxicity of xenobiotics and main mechanisms of realization of their damaging effect are briefly considered. Protective system of a cell is characterized with regard for the peculiarities essential for development of principles of alimentary prophylaxis of cytotoxic effects of foreign compounds. Modern approaches to alimentary modification of the processes of biotransformation of xenobiotics and promotion of protective capacities of a cell are discussed.     

Gramicidin channels: a new mechanism for transmembrane transfer of ions (from high resolution x-ray structural studies of the antibiotic)]

The crystal structure of the membrane-active antibiotic-cyclopeptide gramicidin S complex with urea was determined by the X-ray structure analysis. The gramicidin S molecule possesses an antiparallel beta-structure, its slightly twisted 30-membered cycle has a roughly rectangular form about 4.8 x 13.6 A in size, with the lesser side being formed by the main chain atoms of Phe and Pro residues. The maximum size of the molecule is 22.9 A. A characteristic feature of the molecule is the position of the extended side chains of the Orn residues on one side of the molecular cycle in the form of peculiar "legs--tentacles". One of these legs is "fastened" by the intramolecular H-bond to O atom of the nearer Phe4 residue, the other being free. The distance between the terminal NE atoms of the Orn residues is 5.7 A. The side chains of the Phe and Orn2 residues have trans-orientation, those of the Val, Orn7, Leu residues gauche-orientation. For Val1 and Leu3 side chains statistical disorder of the terminal C atoms is realized. The pyrrolidine rings of the Pro residues adopt Cs-C beta-exo conformation. There are one urea and 20 water molecules per one antibiotic molecule in the structure. The positions of three water molecules are fully occupied, the others with the probability of 0.56-0.20. One of the "water" positions is occupied on 2/3 by water, and on 1/3 by the O atom of the alcohol. There is a complicated system of intra- and intermolecular H-bonds in the structure, with and without the participation of water, alcohol and urea molecules. The gramicidin S molecules, collecting around 3(1) axis according to the left-handed double helix, form the channels whose outside hydrophobic surface is built of the side uncharged radicals, the inside surface being built of the main chain atoms, mainly of the O and N atoms and of the ornithine "tails" with uncharged NE atoms at the termini. The outer diameter of the channel is 29-43 A, inner (without ornithine "tails") is about 12.7 A. At the expense of the change of these "tails" conformation, the inner diameter of the channel filled with water molecules may change from 3.4 up to 6.3 A. Thus, the ions and particles of a rather large size may pass through the channel. The gramicidin channels are discovered and described for the first time. The channels in the crystal structure are close-packed under the hexagonal law.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of carbostimulin on acid-base equilibrium of the blood of racing horses during exertion

The paper deals with possibility to regulate in a proper direction the acid-base state in race horse blood administering carbostimulin at rest and under physical exercises. The preparation is shown to favour an increase in alkaline blood reserves in race hours at rest and to prevent acidotic changes caused by physical exercises. The results obtained show a promising use of carbostimulin for the directed correction of the acid-base state of blood in race horses aimed at increasing the efficiency of the training process.     

Hydrodynamic parameters of native C-reactive protein molecule in a solution

The hydrodynamic properties of the C-reactive protein in solution (pH 6.8) were studied using quasi-elastic light scattering and size-exclusion liquid chromatography. It was shown that the solution containing the C-reactive protein represents a polydisperse system. The values of the translation diffusion coefficient and the apparent molecular weight of the C-reactive protein in solution at pH 6.8 were determined. The values of the translation diffusion coefficient, molecular weight and the hydration radius obtained suggest that the native pentameric C-reactive protein is the major form of the protein in solution at pH 6.8.     

Aggregation of C-reactive protein in solutions at acid pH

The hydrodynamic properties of the C-reactive protein (CRP) at different pH were studied using quasi-elastic light scattering, size-exclusion liquid chromatography, and nonreducing gel electrophoresis. It was shown that a CRP solution at pH 5.0-7.2 presents a polydisperse system the major component of which is the native pentameric CRP. At pH 4.0-4.5, CRP exists in two states having different hydrodynamic properties: the native pentameric form with a molecular mass of 120 kDa and with the hydrodynamic radius of 4.03 nm and high-molecular-weight aggregates with a wide range of their molecular weight distribution. The interaction of the C-reactive protein with monoclonal antibodies to it indicates that conformation-dependent surface epitopes of the protein lose the native structure at pH 5.0-5.5. The aggregation of CRP is an irreversible process, which begins in a narrow pH range of pH 5.0-4.5 and is not accompanied by the dissociation into subunits but is determined by intermolecular interactions of its quasi-native pentamers.     

Domain structure of CAF1M protein from Yersinia pestis. Structure and the role of various domains

The cooperative structure of Caf1M from Yersinia pestis was studied using scanning microcalorimetry, fluorescence, and limited proteolysis. It was shown that, in Caf1M-Hg (a derivative in which the disulfide bond is replaced by an S-Hg-S bond), the first to melt is the N-domain. Then the C-domain melts. After renaturation in a buffer with a low NaCl concentration, only the C-domain is in the native state, and it can be obtained by limited proteolysis. After renaturation in a buffer with a high NaCl concentration, only the N-domain is in the native state, and it can be obtained by limited proteolysis. Both domains have native structure; however, only the N-domain interacts with Cafl (natural substrate for Caf1M).