Tag Archives: actomyosin complex

Influence of heavy metal ions on the ATPase activity of actomyosin complex and myosin subfragment-1 from smooth muscle of the uterus

R. D. Labyntseva, O. M. Bobrovska, O. Ju. Chunikhin, S. O. Kosterin

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: labyntseva@biochem.kiev.ua

The effect of divalent cations – Со2+, Сu2+, Mn2+ and Ni2+ (5 mМ) on the activity of actomyosin complex ATPase and ATPase of subfragment-1 (S1,head) of myosin from smooth muscle of the uterus was studied. It has been shown that Co2+, Mn2+ and Ni2+ inhibited, while Cu2+ activates the enzyme activity of both actomyosin and myosin S1.  Mg and Mn ions had practically no effect on the emission intensity of eosin Y associated with actomyosin, while one could observe the most marked suppression of emission of related fluorescent probe in the presence of Cu  cations and less pronounced suppression in the presence of Co2+.  In the presence of Mn, Co and Ni cations the average hydrodynamic diameter (HD) of actomyosin complex and  of subfragment-1 of the smooth muscle of the uterus is virtually identical to the HD in the presence of Mg2+. In the presence of Cu  cations there is a considerable (ten-fold) increase in the size of the protein particles that may be a result of their aggregation.  The results obtained evidence for the significant changes in the structure and function of the actomyosin complex of the myometrium in the presence of  heavy metals and allow us to assume that the target of the effect of these metals on the contractile proteins is a subfragment-1 of myosin, where the active site of ATPase and actin-binding sites are localized.

ATPase activity of rabbit skeletal muscles actomyosin complex under ultrasound effect

K. O. Medynska, N. Ye. Nurishchenko, L. I. Pelyukh, O. V. Shelyuk

Taras Shevchenko Kyiv National University;
Educational and Scientific Centre “Institute of Biology”, Ukraine;
e-mail: medinkat@ukr.net

Influence of continuous and impulsive ultrasound 0.05; 0.2; 0.4; 0.7 and 1.0 W/cm2 on ATPase activity of rabbit skeletal muscle actomyosin has been investigated in this work. It has been shown that most changes of Mg2+,Ca2+-ATPase activity are observed under 0.2 and 0.4 W/cm2 continuous ultrasound. K+-ATPase activity is inhibited by continuous ultrasound of all intensities studied. Impulsive 2 and 10 ms ultrasound did not change the Mg2+,Ca2+-ATPase activity. While K+-activity is reliably changed only under impulsive 0.7 and 1.0 W/cm2 ultrasound that can be explained by the thermal effect. It has been determined, when studying­ the reconstructed actomyosin with sound troponin complex, that troponin complex is the most ultrasound sensitive constituent of actomyosin.