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.