T. O. Veklich1, A. О. Shkrabak1, R. V. Rodik2, V. I. Boyko2, V. I. Kalchenko2, S. O. Kosterin1
1Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
2Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kyiv;
It was found that calixarene С-107 (5,17-diamino(2-pyridyl)methylphosphono-11,23-di-tret-butyl-26,28-dihydroxy-25,27-dipropoxycalixarene) could effectively reduce Na+,K+-АТРase activity of the myometrium cell plasmatic membranes (the value of the apparent constant of inhibition I0.5 was 33 ± 4 nМ) while it practically did not influence the «basal» Mg2+-АТРase activity of the same membrane. In comparative experiments, we have shown that the model calixarene C-150 – the calixarene «scaffold» (26,28-dihydroxy-25,27-dipropoxycalixarene), and the model compound М-3 (4-hydroxyaniline(2-pyridine)methylphosphonic acid) – a fragment of the calixarene С-107, had practically no influence on the enzymatic activities of Na+,K+-АТРase and Mg2+-АТРаse over a wide range of concentrations. Hence, the influence of calixarene С-107 on Na+,K+-АТРase activity was caused by the joint action of two aminophosphonic substituents on the upper rim of the calixarene bowl. The isomer of calixarene С-107 – calixarene С-160 (5,11-diamino(2-pyridyl)methylphosphono-17,23-di-tret-butyl-26,28-dihydroxy-25,27-dipropoxycalixarene) also did not influence the Na+,K+-АТРase and Mg2+-АТРаse activities of plasmatic membrane of myometrium cells. We carried out molecular modeling of calixarenes C-107 and C-160 and showed differences in interatomic distance between aminophosphonic substituents of mentioned calixarenes. We came to the conclusion that spatial structure of calixarene С-107, namely localization of two aminophosphonic substituents in 5,17 position of the upper rim of this calixarene, is crucial for inhibition of Na+,K+-АТРase activity. Using laser correlation spectroscopy it was found that the 100 µM solution of calixarene C-107 and 2.5% DMSO had microparticles with size range from 100 nm to 10 µm. Plasma membrane vesicles had average hydrodynamic diameter 401 ±?17?nm, but after interaction of these vesicles with calixarene C-107 we have registered the creation of some particles with sizes greater than 10 µm. Therefore membrane vesicles agglutinated to each other and/or to calixarene microparticles.
Key words: Na+,K+-ATPase, Mg2+-ATPase, plasma membrane, smooth muscle cells, myometrium, calixarenes, aminophosphonic acid, spatial structure, hydrodynamic dimensions.
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