Magnetic-Isotope Effects of Magnesium and Zinc in Enzymatic ATP Hydrolysis Driven by Molecular Motors
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CULAR BIOPHYSICS
Magnetic-Isotope Effects of Magnesium and Zinc in Enzymatic ATP Hydrolysis Driven by Molecular Motors V. K. Koltovera, *, R. D. Labyntsevab, and V. K. Karandashevc a Institute
of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia b Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kiev, 01030 Ukraine c Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected] Received November 30, 2019; revised March 4, 2020; accepted March 6, 2020
Abstract—The effects of different magnesium and zinc isotopes on the enzyme activity of myosin subfragment-1 have been explored. The rate of the enzymatic ATP hydrolysis in reaction media enriched with the magnetic isotope, 25Mg, is twice as high as it is in reaction media enriched with the nonmagnetic isotopes, 24Mg or 26Mg. A similar effect of nuclear spin catalysis has been detected in the experiments with zinc isotopes as cofactors of the enzyme. The rate of the enzymatic ATP hydrolysis with magnetic 67Zn increases by 40– 50% compared to that with nonmagnetic 64Zn or 68Zn. The magnetic-isotope effects have been observed at the physiological concentration of magnesium and zinc chlorides (5 mM). The catalytic effect of the magnetic magnesium isotope 25Mg has been revealed in the experiments with Mg-dependent ATPase of myometrial plasma membranes. The magnetic-isotope effects indicate that there is a spin-selective rate-limiting step in the chemo-mechanical process driven by the “molecular motor” due to the energy of ATP hydrolysis and that nuclear spin catalysis causes acceleration of this stage. Some possible mechanisms of the nuclear spin catalysis are discussed. Keywords: nuclear spin catalysis, myosin, ATPase activity, biomolecular motors, bioreliability, magnetic-isotope effect, magnesium, zinc DOI: 10.1134/S0006350920030094
INTRODUCTION Cells and tissues contain atoms of chemical elements, many of which have two types of stable isotopes, magnetic and nonmagnetic. As an example, magnesium has three stable isotopes, 24Mg, 25Mg, and 26Mg with relative contents of 78.7, 10.1, and 11.2%, respectively. The 25Mg isotope is magnetic because its atomic core has a nuclear spin (I = 5/2), which creates a magnetic field. The 24Mg and 26Mg isotopes are nonmagnetic because their nuclei do not have a nuclear spin (I = 0) and, accordingly, do not create a magnetic field. Another common element in nature, zinc, has five stable isotopes, i.e., 64Zn, 66Zn, 67Zn, 68Zn, and 70Zn with relative contents of 48.6, 27.9, 4.1, 18.8, and 0.6%, respectively. Among these, 67Zn is the magnetic isotope (I = 5/2); the other four isotopes are nonmagnetic (I = 0). Magnetic isotopes are also known to create internal magnetic fields, which can exceed the Earth’s magnetic field (≈0.05 mT) by 10 to 100 times at a distance approximately equal to the chemical bond length [1]. Abbreviations: MIE, magnetic-isotope ef
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