[Characteristics of the structure and specificity of aspartyl- and valyl-tRNA-synthetases from muscle tissue of long-fasting rabbits]. / Osobennosti struktury i spetsifichnost' aspartil- i valil-tRNK sintetaz myshechnoi tkani dlitel'no golodavshikh krolikov.

Amino acid compositions of aspartyl- and valyl-tRNA synthetases from the muscles of long-fasting and normal rabbits were studied. Certain differences in amino acid content of fasted and normal rabbits were found. The possibility of incorrect aminoacylation was shown for the tRNA and amino-acyl-tRNA synthetases (ARS) from the muscles of experimental animals. The Km values of incorrect reactions increased with specific and nonspecific amino acids depending on the decreased affinity between specific and nonspecific substrates. At the same time Vmax of these reactions decreased. A presumable decrease in the specificity of ARS isolated from muscles of long-fasting rabbits can be one of the reasons of synthesis of the proteins with the different amino acid composition by the extremal states of the organism.

[Effect of cadmium ions on the rate of the tRNA aminoacylation reaction]. / Vliianie ionov kadmiia na skorost' reaktsii aminoatsilirovaniia tRNK.

Cadmium ions are studied for their effect on the reaction rate of tRNA aminoacylation which was carried out using overall preparations of aminoacyl-tRNA-synthetases (ARSases) isolated from muscles of male rabbits and from three-day pea seedling roots. Cadmium in the concentration of 3 X 10(-5) M is established to accelerate the reaction rate two times as compared to the norm. Other bivalent cations of metals lack this ability.

[Spectral characteristics of muscle aspartyl- and valyl-tRNA- synthetases in normal animals and in an experimental model of prolonged starvation]. / Spektral'nye kharakteristiki myshechnykh asparagil- i valil-tRNK-sintetaz v norme i pri éksperimental'noi modeli polnogo dlitel'nogo golodaniia zhivotnykh.

Conformational differences between asparagyl- and valyl-tRNA synthetases from normal (ARSn) and long-fasting (ARSf) rabbit's muscle were revealed by means of UV fluorescence and differential spectroscopy. The fluorescence spectra indicate more hydrophobic environment of tryptophan residues in the ARSf's at similar quantum yields. The differential absorption spectra reveal the distinctions between tryptophanyl microenvironments for ARS's of different amino acid specificity and for ARSn's and ARSf's of the same specificity. Lower accessibility of tryptophan residues in ARSn's in comparison with ARSf's was shown by selective fluorescence quenching with Cs+ and I- ions. The effect of long-wave shift of fluorescence spectra at the edge excitation was used for studies on microenvironment of chromophors and the rate of the dipole-orientational relaxation of this microenvironment.

[Isolation and purification of aspartyl- and valyl-tRNA-synthetases from muscles of normal and long-fasting rabbits. Structural characteristics and various kinetic parameters]. / Vydelenie i ochistka asparagil- i valil-tRNK-sintetaz iz myshts normal'nykh i dlitel'no golodavshikh krolikov. Strukturnye osobennosti i nekotorye kineticheskie parametry.

Highly purified aspartyl- and valyl-tRNA synthetases were obtained by 6-stage purification from normal and long-fasting rabbit's muscles. The molecular masses of the enzymes are (120 +/- 10) X 10(3). These proteins consist of two subunits (alpha 2-type) with (60 +/- 10) X X 10(3) molecular mass as determined by electrophoresis in SDS polyacrylamide gel. The values of Km for ATP are similar for all the studied enzymes (4.25 divided by 6.48) M X 10(-3) but Km for amino acids differ: (1.22 divided by 3.3) M X 10(-4) for normal and (13.8 divided by 18.9) X M-4 for enzymes from long-fasting rabbits. The molecular activity of the latter increases 2.5-3 fold.

[Spectral characteristics of muscle aspartyl- and valyl-tRNA- synthetases and their complexes with substrates in normal conditions and after prolonged starvation]. / Spektral'nye kharakteristiki myshechnykh aspartil- i valil-tRNK- sintetaz i ikh kompleksov s substratami v norme i posle dlitel'nogo golodaniia.

Spectral characteristics of aminoacyl-tRNA-synthetases (ARSases) isolated from muscles of normal rabbits and of those fasted for a long time were studied by the methods of fluorescence and differential spectroscopy. Fluorescence spectra and differential absorption spectra of the compared proteins evidenced for more hydrophobic surrounding of tryptophanyls and their less accessibility for Cs+ ions in proteins of fasted animals. Interaction of aspartyl- and valyl-tRNA-synthetases from muscles of normal and long-fasted rabbits with substrates is accompanied by the essential quenching of tryptophan fluorescence of ARSases. Equilibrium constants of substrate binding calculated from the fluorescence quenching curves are higher for specific amino acids than for non-specific ones. The effect of a long-wave shift of fluorescence spectra under marginal excitation of tryptophan residues was used to determine structural differences of enzymes in norm and under fasting and to find their structural peculiarities during formation of aminoacyl adenylate. Aminoacyl-tRNA-synthetases (ARSases) are key enzymes of the protein biosynthesis. High specificity of their interaction with substrates is the basis for the accuracy of genetic information implementation, namely translation of the genetic code. Molecular mechanisms of substrates "recognition" by ARSases are the objects of great attention of researchers.

[Amino-tRNA-synthetase activity of rabbit muscles in fasting and aging]. / Kharakteristika aminoatsil-t-RNK-sintetaznoi aktivnosti myshts krolikov pri golodanii i starenii opganizma.

The aminoacyl-tRNA-synthetase activity of muscular soluble fraction was studied in normal rabbits, in those fasting for a long period and old rabbits. A rigion of linear dependence is found for the initial rate of the tRNA aminoacylation reaction on the concentration of the enzymic preparation and also on the substrate amount. Having valuated the initial rate of the aminoacylation reaction, the asparagil- and valyl-tRNA-synthetase activities of muscles were determined in normal rabbits, in those fasting for a long period and in old rabbits. The data obtained evidence for an increase of the studied activities in the muscles of the fasting animals and for their decrease in old animals.

[Effect of fasting on aminoacylation of tRNA from rabbit muscles]. / Vliianie golodaniia na aminoatsilirovanie TRNK iz myshts krolikov.

The aminoacylation of tRNA from muscles was studied in the fasting rabbits. It is shown that under equal conditions of incubation the intensity of the process is higher in the fasting animals. It may be a result of an increase in the content or activity of leucil-tRNA-synthetase in muscles of the fasting rabbits, that is testified by the evidence on the level of aminoacylation in heterologous systems.

[Conformational changes in rabbit muscle aldolase under normal conditions and following prolonged starvation]. / Konformasiini vidminnosti al'dolazy m'iaziv kroliv u normi ta za tryvaloho holoduvannia

The experiments were aimed at studying conformation differences of muscle aldolase in normal rabbits and those fasting for a long time and at finding the areas of polypeptide chains affected by the changes. For this purpose the difference, temperature- and solvent-perturbation spectra of the compared proteins were examined. On the basis of the data obtained on the same amount of chromophore groups in both proteins a conclusion is drawn on a more hydrophobic surrounding of tyrosine and tryptophan residues in aldolase of the long-fasting animals. When determing the content of the tyrosine and tryptophan surface residues an increase (from 13 to 21) was found in the number of the tyrosine residues in aldolase of the long-fasting animals. An assumption is advanced on localization of the primary structure changes in the molecule sites rich in chromophore groups or those located closer to them.

[Changes in the primary structure of rabbit muscle aldolase under the influence of valine against a background of prolonged fasting]. / Zminy pervynnoï struktury aldolazy míaziv kroliv pid vplyvom valinu na foni tryvaloho holoduvannia

The primary structure of the muscle aldolase molecule was studied as affected by semilethal doses of valine administered the abdominal cavity of the rabbits after a long fasting. It is established that in spite of differences in the amino acid composition of the protein, uniformity of the peptides distribution in the process of bromo-cyanogen fragments elution and the total amount of amino acid residues in the identical fragments are maintained. Changes are found only in the point-replacements by amino acids in C-fragment of the molecule (asparagine is replaced by valine and threonine by serine).