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N S Shelud'ko

Publications and source records attributed to N S Shelud'ko.

At least 19 recordsLinked to original sources
PubMed1993

[Change in the size of particles in actomyosin suspensions during superprecipitation].

Changes in the properties of natural actomyosin suspensions, such as turbidity, light scattering, volume concentration, particle size and particle size distribution during superprecipitation (SPP) of actomyosin in media of different compositions have been investigated. Two sets of changes indicating the existence of two SPP types--the "immediate" SPP characterized by a rapid one-step rise in turbidity and the "spontaneous" SPP, when the slow increase in turbidity follows the clear phase, have been revealed. In both cases the mechanism of the increase in the suspension turbidity is assumed to be similar and is conditioned by an increase in the refraction index (density) of the particles; however, the ways of formation of dense particles are different. During the "immediate" SPP, the particle density increases due to particle striction, whereas during the "spontaneous" SPP dense particles are formed as a result of ordered lateral association of myosin and actin filaments.

Actomyosin↗
PubMed1990

Optical properties of myofibril and actomyosin suspensions. 1. Angular dependence of light scattering by myofibril suspensions and its changes under myofibril contraction.

The angular dependence of light scattering by myofibril suspensions has been measured within the angle range of 0.05 degrees and 160 degrees at different suspension concentrations and wavelengths. Angular diagrams appear to be highly asymmetry, and extended forward in the direction of the primary light propagation. A suspension with the concentration of 0.1 mg/ml at 550 nm scatters, for example, no less than 90% light at angles of less than 6 degrees. The scattering diagram becomes less asymmetric upon increasing the suspension concentration and decreasing the wavelength of the light. Upon addition of MgATP in the presence of Ca2+, a myofibril suspension undergoes two kinds of optical change, namely, fast ones corresponding to myofibril contraction, and slow ones correlating with the subsequent aggregation of the contracted myofibrils. Fast changes are believed to be due to the increase of the refractive index of the contracting myofibrils, and slow changes to the increase in the size of the suspension particles resulting from aggregation. Light scattering by myofibril and actomyosin suspensions seems to be due not only to the particle as a whole, but also to its internal structure.

Actomyosin↗
PubMed1989

[The causes of the nonuniform thermostability of Mg-ATPase and of the contractility of muscle models].

With longer periods of preliminary heat-treatment of actomyosin suspension the decrease in the rate of superprecipitation (SPP) is followed by that in the extent of SPP, and, finally, in the Mg-ATPase activity. A similar uncoupling of mechanical and enzymatic activities is observed when the ratio between the native and the inactivated myosin in reconstructed actomyosin varied. This uncoupling is supposed to result from the formation during heat-treatment of myosin bridges incapable of dissociating in the presence of Mg-ATP. The bridges affect largely the mechanical properties of actomyosin, and in a lesser degree, its enzymatic properties.

Actins↗
PubMed1986

[Changes in the mechano-chemical properties of actomyosin during desensitization].

The loss of Ca2+-sensitivity by natural actomyosin (desensitisation) after treatment with low ionic strength solutions results in marked deceleration of protein superprecipitation. This phenomenon is not due to the removal of minor proteins, since a similar effect was observed during "desensitisation" of synthetic actomyosin containing only myosin and actin. However, addition to desensitised actomyosin of tropomyosin, especially in combination with alpha-actinin markedly restores the initial parameters of superprecipitation and ATPase activity. It was assumed that desensitisation has a direct modifying influence on actomyosin, whose effect is weakened in the presence of tropomyosin and alpha-actinin.

Actinin↗
PubMed1983

[A high molecular proteolysis-resistant actin fragment].

The proteolysis-stable actin fragment (m. w. 36300 as determined by SDS polyacrylamide gel electrophoresis) was obtained by actin treatment with a non-identified bacterial protease. This fragment is larger than the trypsin-stable actin fragment and is similar to the unstable trypsin intermediate fragment. The obtained actin fragment is not polymerized, does not activate the ATPase activity of myosin and does not form a superprecipitating complex with it. Thus, the functional properties of actin are lost during the split-off of a relatively small, apparently, the N-terminal part of the polypeptide chain.

Actins↗
PubMed1975

[Protein makeup of rabbit myofibrils determined by a disc eletrophoretic method in the presence of sodium dodecyl sulfate].

The protein subunit composition of isolated myofibrils of rabbit skeletal muscle is studied by polyacrylamide gel disc-electrophoresis in the presense of sodium dodecyl sulfate (SDS). The method of disc-SDS-electrophoresis is described in detail. The electrophoretic patterns of SDS-solubilized myofibrils obtained by disc-SDS-electrophoresis and by SDS-electrophoresis in continuous buffer system according to Weber and Osborn are compared. The former results in a markedly improved resolution and allows to discover some additional protein components, the origin of these additional components being discussed. A standard curve is given for determination of polypeptide chain molecular weights by disc-SDS-electrophoresis.

Animals↗
PubMedDate not supplied

[N-ethylmaleimide inhibits polymerization of myorod, a contractile protein of thick filaments of molluscan smooth muscles].

The effect of N-ethylmaleimide on the polymerization of myorod, a protein of molluscan smooth muscles, which is colocalized with myosin on the surface of paramyosin core of thick filaments and is a product of the alternative splicing of the gene of heavy myosin chains, was studied. It was shown that myorod modified by N-ethylmaleimide completely loses the polymerization ability but acquires the ability to aggregate in the presence of Mg2+. At the same time, treatment of molluscan myosin with N-ethylmaleimide did not affect its polymerization. It was supposed that the effect of N-ethylmaleimide on myorod polymerization is related to the modification of the myorod SH domain containing Cys722.

Actin Cytoskeleton↗
PubMedDate not supplied

[Polymerization of myorod, a surface protein of thick filaments of molluscan smooth muscle].

The study is concerned with the polymerization of myorod, a protein from thick filaments of molluscan smooth muscles, which is an alternative product of the gene of myosin heavy chains. The dependences of the properties and polymer structure of myorod on the conditions of its formation were investigated. It was shown that myorod loses the ability to form viscous polymers after proteolytic removal of the unique sequence. It was supposed that the specificity of polymerization of myorod are determined by its unique N-terminal sequence.

Animals↗
PubMedDate not supplied

[Aggregation of isolated myofibrils stimulated by their contraction. II. Aggregation mechanism].

Aggregation of contracted myofibrils was studied as a function of experimental conditions at myofibril contraction. The aggregation rate increased at higher concentrations of suspensions and at increased ionic strength of the medium to achieve the maximum at 0.1 M KCL in the last case. The aggregate sizes grow with an increase of ionic strength and concentration of MgATP and reduce with addition of F-actin. Aggregation of myofibrils develops only in the case of their complete or significant contraction. It was suggested that aggregation is stimulated by dehydration of myofibril at contraction.

Actins↗
PubMedDate not supplied

[Aggregation of isolated myofibrils stimulated by their contraction. I. Origin of the second phase of optical changes during myofibril contraction].

Aggregation of contracted myofibrils was shown to be responsible for spontaneous: slow reduction of optical density of myofibril suspension on the final stage of their contraction. This effect faded with an increase in light wavelength, with increased angle of view of the photocell and diminished sizes of myofibrils.

Actomyosin↗
PubMedDate not supplied

[Angle diagrams of light scattering in the suspension of isolated myofibrils in native, contracted and relaxed states].

An angle diagram of light scattering of myofibril suspensions was extremely asymmetric in the range of 0.05 to 10 degrees. The extent of asymmetry increased at relaxation and sharply decreased at contraction of myofibrils. Angle diagrams for myofibril light scattering calculated according to the approximate formulae of Mie theory, were close to those obtained in the experiment. It was shown that a high extent of asymmetry of calculated diagrams is determined by a low refractive index of myofibrils rather than by great dimensions of myofibrils. It is supposed that changes in the shape of scattering diagram and in other optical characteristics of myofibril and actomyosin suspensions associated with changes in their functional states depend mostly upon changes in the inner arrangement of particles rather than in their dimensions.

Animals↗
PubMedDate not supplied

[Interrelated effects of ATP and ionic strength on Ca2+-sensitivity of isolated myofibrils].

Ability of isolated myofibrils for relaxation was studied in a medium with KCl concentrations of 6 to 250 mM with ATP content varying from 0.01 to 1.0 mM. It was shown that myofibrils can relax at all the studied values of the ionic strength, but ATP concentration required for the relaxation is to increase with decreasing the ionic strength A stable state of Ca2+-sensitive system of myofibrils is maintained at approximately the same values of ATP and KCl concentrations. A possible mechanism of this phenomenon is discussed.

Adenosine Triphosphate↗
PubMedDate not supplied

[Influence of C-protein on mechano-chemical properties and structure of reconstituted actomyosin].

C-protein on the mechano-chemical properties (ATPase activity and superprecipitation) of actomyosin systems has been investigated. The presence of C-protein in AM-complexes has been shown to decrease the rate of superprecipitation (SPP) and simultaneously increase the ATPase activity. Both effects of C-protein are dependent on its quantity in the system. Tropomyosin decreased considerably but does not eliminate completely the inhibitory influence of C-protein on the SPP. Electron microscopy does not reveal considerable structural differences in the initial AM-complexes depending on the presence or absence of C-protein. It is supposed that the discovered effects of C-protein on the behaviour of AM-systems are determined by the fine local structural and (or) charge changes produced by C-protein in the region of myosin cross-bridges, which in its turn results in a modification of the actin-myosin interaction. Possible participation of C-protein in the regulation of the interaction of thin and thick filaments in the muscle is discussed.

Actomyosin↗
PubMedDate not supplied

[Interaction of alpha-actinin and tropomyosin with F-actin].

The interaction of alpha-actinin, F-actin and tropomyosin has been investigated by using electron microscopy, SDS-gel electrophoresis and viscosimetry. It was shown that the temperature dependence of the interaction with F-actin was similar for alpha-actinins, isolated from the muscle of warmblooded animal (rabbit skeletal muscle) and from muscle of cold--blooded ones (cross striated part of the adductor of scallop Patinopecten yessoensis). The temperature rise from 0 degrees C to 37 degrees C results in a decrease of the affinity of alpha-actinin to F-actin. Tropomyosin decreases the amount of alpha-actinin bound to F-actin at 37 degrees C, but does not dislodge it completely from F-actin filaments. In this case the alpha-actinin binding also occurs along the entire length of the F-actin. It has also been shown that at 0 degrees C alpha-actinin and tropomyosin interact with F-actin independently of each other. The data obtained attest that tropomyosin and alpha-actinin have different binding sites on F-actin. The temperature and tropomyosin regulate only the amount of the bound alpha-actinin, but not its localization on the actin filament, as it was earlier supposed. These data allow one to conclude that the localization of alpha-actinin in Z-disk of cross-striated muscle can be determined neither by physiological temperature nor the presence of tropomyosin.

Actinin↗
PubMedDate not supplied

[Alpha-actinin of Primor'e scallop striated muscle. Physico-chemical properties].

A protein with chain weight of about 90,000 Dalton (MP-90) was isolated from the cross-striated adductor muscle of the scallop Patinopecten yessoensis. The Physicochemical properties of MP-90 and its interaction with actin were studied in comparison with those of alpha-actinin of rabbit skeletal muscle. The data obtained allow us to conclude that this isolated protein is alpha-actinin of cross-striated adductor muscle of scallop Patinopecten yessoensis.

Actinin↗