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D I Levitskiĭ

Publications and source records attributed to D I Levitskiĭ.

At least 19 recordsLinked to original sources
PubMed1995

[The effect of modifying the lysine-83 residue on the thermal stability of myosin subfragment 1 and changes in it caused by nucleotide binding].

The effects of trinitrophenylation of lysyl residues of rabbit skeletal myosin subfragment 1 (S1) on thermal denaturation of S1 in the absence of nucleotides, in the presence of ADP and within S1 complexes with ADP and Pi analogues, orthovanadate (Vi) or beryllium fluoride (BeFx), have been studied by differential scanning calorimetry. It has been shown that lysyl trinitrophenylation significantly affects the thermal stability of S1, changes its domain structure, promotes the decomposition of S1.ADP.Vi and S1.ADP.BeFx complexes, and strongly prevents the structural changes in the S1 molecule induced by the formation of the S1.ADP.Vi complex without any effect on the thermal stability of S1 within S1.ADP and S1.ADP.BeFx complexes. It has been demonstrated that the effects of trinitrophenylation on the S1 structure are mainly due to specific modification of the epsilon-amino group of the Lys-83 residue.

Animals↗
PubMed1991

[Myosin head structure].

The current data and concepts of the structural organization of the head of myosin, one of the major muscle proteins, are reviewed. The primary structure of the isolated myosin head (myosin subfragment-1) heavy chain and localization in it of sites and groups responsible for the binding and hydrolysis of ATP and myosin interaction with actin, are considered. Evidence is given of reciprocal spatial distribution of these sites and their localization on the myosin head surface. Some present-day concepts on the domain organization of the myosin head and its changes occurring during binding and hydrolysis of ATP, are discussed. A model describing the folding of the heavy and light chains in the myosin head is proposed.

Adenosine Triphosphate↗
PubMed1991

[Interaction of isoforms of subfragment-1 of myosin, containing fluorescently labelled alkaline light chains, with muscle fiber actin].

Using polarization microfluorimetry, the interaction of myosin subfragment 1 (S1) isoforms containing alkali light chains A1 and A2 respectively (S1(A1) and S1(A2] with F-actin of single glycerinated rabbit skeletal muscle fibers was studied. The alkali light chains of S1 were substituted by reassociation for A1 or A2 chains modified by a fluorescent label (1.5-IAEDANS) at the single SH-group located in the C-terminus. It was found that in S1(A1) bound to muscle fiber F-actin the mobility of the fluorescent label is lower than in S1(A2). At the same time the S1(A1) and S1(A2) interaction with F-actin induces similar changes in polarized fluorescence of rhodamine linked to falloidine which, in turn, is specifically bound to F-actin. It is concluded that the both S1 isoforms bind to F-actin and produce similar effects on the conformational state of actin filaments in muscle fibers. Local differences between S1(A1) and S1(A2) seem to be due to the interaction of the N-terminus of A1 within S1(A1) with the C-terminal region of actin.

Actins↗
PubMed1987

[Effect of phosphorylation of myosin light chains on the interaction of myosin minifilaments with F-actin].

The effect of phosphorylation of light chains-2 (LC2) of rabbit skeletal muscle myosin on the interaction of myosin minifilaments with F-actin as well as on the actin-stimulated Mg2+-ATPase of minifilaments was studied. It was shown that in the absence of KCl the degree of F-actin-induced stimulation of myosin minifilament Mg2+-ATPase with phosphorylated LC2 exceeds 2-4-fold that with unphosphorylated LC2. Phosphorylation of LC2 considerably increases the rate of actin-stimulated Mg2+-ATPase reaction of myosin minifilaments but exerts only a very weak influence on the affinity of minifilaments for F-actin. After addition of KCl the differences in the actin-stimulated Mg2+-ATPase activity disappear in a great degree; in the presence of 50 mM KCl they do not exceed 50%. It was assumed that the observed specific influence of LC2 phosphorylation on the kinetic parameters of actin-stimulated Mg2+-ATPase reaction of myosin minifilaments is due to unique properties of the minifilaments (e.g., their ability to ordered self-assembly as a result of interaction between the heads of myosin molecules) which reflect their structural peculiarities.

Actins↗
PubMed1987

[Changes in the structural state of myosin filaments in glycerol-treated fibers of rabbit skeletal muscles induced by phosphorylation of myosin light chains].

Using the polarization microfluorimetry method, it was demonstrated that the increase in the degree of phosphorylation of myosin light chains (LC2) in extended single glycerinated fibers from rabbit psoas muscle changes the anisotropy of polarized fluorescence both tryptophan residue in the rod parts of the myosin molecule and the fluorescent label-N (iodoacetyl-aminoethyl)-5-naphthylamine-1-sulfonate (1,5-IAEDANS) bound to the SH1-group in myosin molecule heads. The changes in fluorescence anisotropy during LC2 phosphorylation were observed, when the measurements were performed only in the presence of 5 mM MgCl2. It was suggested that in the presence of MgCl2 the phosphorylation of LC2 associated with myosin heads changes their orientation and causes conformational shifts in the myosin filament core.

Animals↗
PubMed1986

[Phosphorylation of light chains of myosin from rabbit skeletal muscles affects the type of conformation changes of F-actin induced by heavy meromyosin].

The changes in F-actin conformation in myosin-free single ghost fiber induced by the binding of heavy meromyosin (HMM) with dephosphorylated or phosphorylated light chains-2 (LC2) have been studied by measuring intrinsic tryptophan polarized fluorescence of F-actin. It has been found that at low concentrations of Ca2+ (pCa greater than or equal to 8), the binding of HMM with dephosphorylated LC2 to F-actin in ghost fibres increases, whereas the binding of HMM with phosphorylated LC2 decreases the anisotropy of polarized tryptophan fluorescence. The effect is reversed at high concentrations of Ca2+ (pCa = 5). It has been assumed that this effect of myosin light chains phosphorylation may be due to its influence on the type of myosin head binding to F-actin.

Actins↗
PubMed1984

[High sensitivity to Ca2 ions of the conformational changes of F-actin, induced by the myosin 1 subfragment].

The effects of Ca2+ on conformational changes of ghost muscle fiber F-actin induced by binding of isolated rabbit skeletal muscle myosin heads (myosin subfragment 1, S1) were investigated. The changes in F-actin induced by binding of S1 to F-actin were followed by the changes in polarized tryptophan fluorescence of F-actin. It was found that the conformational changes in F-actin during the binding of S1 free of DTNB-light chains are insensitive to the changes in Ca2+ concentration. The binding of native S1 containing native DTNB-light chains induces Ca2+-sensitive conformational changes in F-actin. These changes are observed at Ca2+ concentrations of 10(-7)-10(-6) M. Such high sensitivity to Ca2+ exceeds that of S1 containing native DTNB-light chains. It was assumed that the Ca2+-sensitive conformational changes in F-actin induced by myosin head binding reflect the structural changes in thin actin filaments. These changes seem to occur in muscle fibers during the initiation and development of contraction and may be related to the control of vertebrate skeletal muscle contraction by Ca2+.

Actins↗
PubMed1982

[Study of cation binding to myosin subfragment I using the fluorescent probe Eu3+].

It was shown that binding of the cation Eu3+ to myosin subfragment I (SI) results in fluorescence with a maximum at 595 nm which is increased as EuCl3 concentration rises. The ATPase activity of SI is simultaneously enhanced. An addition of bivalent cations (Ca2+ and Mg2+) causes quenching of fluorescence of the bound Eu3+ by 8-12%, which corresponds to Eu3+-ATPase inhibition by Mg2+. At low (down to 0.1 mM) concentrations of Eu3+ no fluorescence quenching by Mg2+ or Ca2+ takes place; under these conditions Mg2+ activate ATPase of SI in the presence of Eu3+. Eu3+ activate SI ATPase in the presence of low (down to 0.1 mM) concentrations of Ca2+, but exerts an inhibition action at high concentrations of Ca2+. NaCl does not affect the fluorescence intensity of bound Eu3+ but considerably inhibits the ATPase activity of SI in the presence of EuCl3. An existence of a bivalent cation binding site in the vicinity if the SI active center is postulated. Eu3+ whose ionic radius is close to that of Ca2+ interacts with protein surface and occupies this site as well, thus determining the activation of SI ATPase and can be replaced from it by Ca2+ and Mg2+, but not by Na+. Hence bivalent and monovalent cations are bound at different sites. The data obtained provide another proof in favour of a hypothesis suggesting that the regulation of myosin ATPase activity by bivalent and monovalent cations can be mediated by binding of these cations to the protein.

Animals↗