[Distribution of tryptophan groups in molecules of troponin T, troponin I-troponin T complex, and alpha-actinin]. / Raspredelenie triptofanovykh ostatkov v molekulakh troponina T, kompleksa troponin I-troponin T i al'fa-aktinina.

The method of fluorescence quenching was used to experimentally determine the distribution of tryptophan residues in molecules of troponin T, troponin T-troponin I complexes, and alpha-actinin. Iodide and cesium ions, and acrylamide were used as quenchers. It was shown that cesium ions decrease the fluorescence intensity of troponin T and its complex with troponin I by the mode of dynamic quenching. For alpha-actinin such a dynamic quencher is anionic iodide. By using the modified Stern-Volmer equation, the quenching was found to be about 90% of total fluorescence intensity for troponin T, approximately 70% for the troponin T-troponin I complexes, and 20% for alpha-actinin. The penetration of cesium ions to tryptophan 206 (tryptophan 204) in the troponin T-troponin I complex is hindered, probably due to the participation of this tryptophan in the formation of bonds between troponin subunits.

[Conformational transitions in myosin cross-bridges during the mechanochemical act]. / O konformatsionnykh perekhodakh v miozinovykh mostikakh v protsesse me khanokhimicheskogo akta.

The investigations of the molecular bases of muscle contraction posed the following question: in which part of the myosin cross-bridge, the head or the fibrillar part, the conformational changes occur that lead to the generation of force. The paper deals with experimental and theoretical data that are in some way related to the solution of this question. Based on the analysis of recent data, an alternative pattern of ATP hydrolysis-coupled structural alternations in the myosin bridge during the mechanochemical act is proposed.

[Site-specific photomodification of nucleic acids with arylazide and perfluoroarylazide oligonucleotide derivatives. II. Specificity in relation to nucleosides]. / Komplementarno adresovannaia fotomodifikatsiia nukleinovykh kislot arilazidnymi i perftorarilazidnymi proizvodnymi oligonukleotidov. II. Issledovanie spetsifichnosti po otnosheniiu k nukleozidam.

Oligonucleotide reagents bearing aromatic azido groups of different structures were shown to be suitable for nucleoside specific photomodification of nucleic acids. Modification of the pentadecanucleotide targets d(TAAGTGGAGTTTGGC), d(TAAGTGGAAAAAAAA), d(TAAGTGGACCCCCCC) and d(TAAGTGGATTTTTTT) was investigated with reagents d(UCH2OCH2CH2NHCORCCACTT) carrying a photoactive group R(R1-n-azidotetrafluorophenyl-reagent (I), R2-2-nitro-5-azidophenyl-reagent (II) and R3-n-azidophenyl-reagent (III)) at C-5-modified deoxyuridine. Photomodification did not exceed 5% for the targets in case of reagent (III); the modification extent was 25-50% depending on the target sequence for reagent (II); reagent (I) with perfluoro azido group was the most effective, that provided 60-70% of modification. Reagents (I) and (II) were found to be sensitive to the nucleoside sequence of the target: the most vulnerable sites for reagent (I) and (II) were guanine and cytosine residues, respectively. These bases were modified predominantly when being adjacent to the addressed site of the target.

[Effective complementarily-addressed photomodification of nucleic acids by oligonucleotide derivatives, containing aromatic azido groups]. / Effektivnaia komplemntarno adresovannaia fotomodifikatsiia nukleinovykhkislot proizvodnymi oligonukleotidov, soderzhashchikh aromaticheskuiu azidogruppu.

Highly effective site-specific photomodification of a DNA-target was carried out with oligonucleotide reagents carrying aromatic azido groups. Oligonucleotide derivatives with a photoactive function R on the 5'-terminal phosphate and at C-5 atom of deoxyuridine were synthesized: R1NH(CH2)3NHpd(TCCACTT) and d(ULNHRCCACTT), where R1 is p-azidotetrafluorobenzoyl, R2 is 2-nitro, 5-azidobenzoyl, R3 is p-azidobenzoyl; LNH = -CH2NH-, -CH2OCH2CH2NH- or -CH2NHCOCH2CH2NH-. The prepared compounds form stable complementary complexes and effect site-specific photomodification of the target DNA. The modification of pentadecanucleotide d(TAAGTGGAGTTTGGC) with the reagents was investigated. Maximum extent of modification strongly depended on the reagent's type, the photoreagent with R1 being the most effective. Whatever the binding site was, this agent provided a 65-70% modification in all cases except LNH = -CH2NH-, when the yield was twice lower. For the reagents bearing R1 the modification sites were identified. Selective modification at the G9 residue was detected in the case of LNH = -CH2OCH2CH2NH- and when a photoactive group was linked to the terminal phosphate.

[Transitions of the left poly-L-proline II helix-right alpha helix type in the regions of myosin subfragment S2 of cross-striated muscle as a possible conformational basis for a mechanical-chemical act]. / Perekhody tipa levaia spiral' poli-L-prolin II-pravaia alpha-spiral' v uchastkakh subfragmenta S2 miozina poperechnopolosatoi myshtsy kak vozmozhnaia konformatsionnaia osnova mekhano-khimicheskogo akta.

Local conformational states of fibrous fragments of myosin molecules from striated muscle have been studied. Analysis of the amino acid sequences of the rat embryonic skeletal muscle myosin heavy chain and the nematode myosin heavy chain have been performed with the aim to estimate the influence of electrostatic interactions on secondary structure stability of these fragments. The heterogeneity of stability of alpha-helical conformation along the fibrous fragment have been found on the basis of estimation of interaction between side group charges and between side group charges and main chain charges. Periodically located short sections have been found in the N-terminal half of the myosin rod where clusters of Asp and Glu destabilize alpha-helical structure being ionized. Changes of the distribution of charges near the latter sections bring about conformational transitions from left-handed polyproline II helix to right alpha-helix or vice versa. The new scheme of orientation of fibrous part of the cross-bridge in relation to the thick filament for various stages of muscle contraction process suggests asynchronous character of transitions in the different sites. It may be proposed that existence of alteration left- and right-helical fragments in N-terminal half of fibrous part of heavy myosin chain determines zigzag form of this part of myosin molecule in resting muscle. A model of the cross-bridge movement in the course of ATP hydrolysis has been suggested.

Primary structure of the cDNA 5'-terminal region encoding the N-terminal domain of the rabbit muscle alpha-actinin subunit.

A number of cDNA clones have been obtained in summary encoding the N-terminal domain containing 286 amino acid residues of the rabbit skeletal muscle alpha-actinin subunit. Alpha-Actinin cDNA clones were isolated from specific cDNA libraries using the primer extension method for synthesis of the first cDNA chain. A strong stop signal for AMV reverse transcriptase in the 5'-terminal region of mRNA of alpha-actinin was found. It seems there is a G+C rich region (93% G+C nucleotides) including a continuous sequence of 23 G and C nucleotides encoding 6 glycine residues.

[Investigation of the functional properties of domains of alpha-actinin]. / Issledovanie funktsional'nykh svoistv domenov alpha-aktinina.

The role of domains in rabbit skeletal muscle alpha-actinin was investigated. The binding center of alpha-actinin containing F-actin is localized in the N-terminal domain, while the C-terminal domain provides for dimerization of the protein molecule. A model of structural organization of the alpha-actinin was proposed, according to which the subunits within the molecule are oriented so that the N-terminal domains localized on the opposite sides of the protein molecule form the binding centers of alpha-actinin with F-actin.

[Organization of simple sequences in the Drosophilia melanoga ter genome]. / Organizatsiia prostykh posledovatel'nostei v genome Drosophilia melanogaster.

Fragments of Drosophila melanogaster DNA that intensively hybridize with simple sequences poly[(dG-dT).(dC-dA)], poly[(dA).(dT)] and poly[(dG-dA).(dC-dT)] were cloned. The first two types of simple sequences are organized in these clones as separated stretches of moderate length, repeated many times within 12-15 kb. Each cluster contains only one type of the simple sequences and originates from a unique in the genome. In contrast, poly[(dG-dA).(dC-dT)] occurs in the genome as several isolated motifs.

[Domain organization of alpha-actinin from the rabbit skeletal muscle]. / Domennaia organizatsiia alpha-aktinina skeletnoi myshtsy krolika.

Limited trypsinolysis of native alpha-actinin by trypsin was carried out. This procedure resulted in the formation of two large fragments with Mr of 30 and 70 kD which cover almost the whole subunit of alpha-actinin. Using the sedimentation equilibrium method, it was demonstrated that the bisubunit structure of alpha-actinin is provided for by C-terminal fragments of the subunits. Data from circular dichroism analysis suggest that the fragments formed are independent structural units, i.e., domains.

[Fragments of limited trypsinolysis of native alpha-actinin]. / Fragmenty ogranichennogo tripsinoliza nativnogo alpha-aktinina.

Incubation of native alpha-actinin with trypsin leads to the formation of intermediate fragments that are quite resistant to further enzyme action (M 98, 85, 80, 70, 64, 55, 38, 30, 15 kDa). Analysis of these fragments made it possible to elucidate the course of trypsinolysis and to localize the fragments in the polypeptide chain of alpha-actinin subunit.

[Limited trypsinolysis of alpha-actin and the distribution of sulfhydryl groups in the molecular fragments]. / Ogranichennyi tripsinoliz al'fa-aktina i raspredelenie sul'gidril'nykh grupp po fragmentam molekuly.

Incubation of alpha-actinin with trypsin leads to the formation of several fragments with molecular weight of 55 000, 38 000, 30 000 and 15 000 which are rather resistant against further proteinase action. Two from five exposed cysteine residues modified by N-ethylmaleimide in the polypeptide chain of the subunit are located in the 55 000 fragment, one in the 30 000 fragment, and the remaining two appear to belong to those parts of the polypeptide chain that are subject to degradation to small peptides under the action of trypsin. Masked SH-groups are localized to the 30 000 fragment.

[Connectin from muscle cells is a collagen protein]. / Konnektin iz myshechnykh kletok iavliaetsia belkom kollagenovogo tipa.

By X-ray analysis a collagen-like structure was observed in the muscle protein connectin . Hydration of species gives a clearer diffraction pattern, which is characteristic of the collagen-like structures. The functional role of connectin should consist in the fixation of maximum length of muscular cells.

[Influence of monovalent cations on the ATP activity and superprecipitation of actomyosin]. / Vliianie odnovalentnykh kationov na ATFaznuiu aktivnost' i superpretsipitatsiiu aktomiozina.

Dependence of ATP activity and superprecipitation of reconstructed actomyosin on ionic strength, pH and ionic radius of the monovalent cations at different temperatures has been investigated. It is established that the optimum of ATP activity and superprecipitation of synthetic actomyosin at the presence of different monovalent cations was in the ionic strength range 0.09-0.1, in the pH range--7.5-8.0. The monovalent cations according to their efficiency are arranged in the following order: Na+ greater than or equal to K+ greater than Rb+ greater than Li+ and Cs+.

[Isolation and certain properties of minor protein P55 inhibiting myosin and actinomyosin ATPase activity]. / Vydelenie i nekotorye svoistva minornogo belka P55, ingibiruiushchego ATFaznuiu aktivnost' miozina i aktomiozina.

A method of minor protein P55 isolation from extract of soluble proteins of A-zone of the sarcomere from rabbit skeletal muscle is described. It is shown that this protein inhibits Ca2+-ATPase of myosin and Mg2+-ATPase of reconstructed actomyosin, but it does not affect superprecipitation of actomyosin. The molecular weight which is determined by mobility and its polypeptide chain polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate is about 35 000 dalton.