Divalent cation inhibition of barley root plasma membrane-bound Ca2+-ATPase activity and its reversal by monovalent cations |
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Authors: | Charles R Caldwell Alfred Haug |
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Institution: | MSU-DOE Plant Res. Lab., Michigan State Univ., East Lansing, MI 48824, USA. |
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Abstract: | The inhibitory action of divalent cations on the Ca2+-ATPase activity of a plasma membrane-rich microsome fraction isolated from the roots of barley ( Hordeum vulgare L. cv. Conquest) was investigated. Using electron paramagnetic resonance spectroscopy to measure cation-induced changes in membrane lipid properties, it was demonstrated that certain divalent cations (Ca2+, Cd2+, UO2+2) inhibit the Ca2+ ATP-ase by restriction of lipid polar head group mobility and not by alteration of membrane surface potential. Monovalent cations which stimulate the Ca2+-ATPase of barley roots (Na+, K+, ethanolamine HCl) can also reverse the Ca2+-ATPase inhibition by Cd2+. The degree of Na+ reversal of Cd2+-induced Ca2+-ATPase inhibition was influenced by the nature of the anion. |
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Keywords: | Cation-lipid interaction electron paramagnetic resonance lipid mobility monovalent cation stimulation spin-labelled probe |
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