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Mn<sup>2+</sup> transport by Ca<sup>2+</sup>‐ATPase of sarcoplasmic reticulum
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- Shin‐Ichiro Yonekura
- Institute of Molecular and Cellular Biosciences University of Tokyo Japan
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- Chikashi Toyoshima
- Institute of Molecular and Cellular Biosciences University of Tokyo Japan
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Description
<jats:p>Ca<jats:sup>2+</jats:sup>‐ATPase of sarcoplasmic reticulum is known to pump Mn<jats:sup>2+</jats:sup> in addition to Ca<jats:sup>2+</jats:sup>, but whether its transport mechanism is identical to that of Ca<jats:sup>2+</jats:sup> is ambiguous. To clarify, we examined, by atomic absorption spectroscopy, competition between Mn<jats:sup>2+</jats:sup> and Ca<jats:sup>2+</jats:sup> in active transport using vesicles of sarcoplasmic reticulum (SR). Here, we demonstrate that Ca<jats:sup>2+</jats:sup>‐ATPase transports Ca<jats:sup>2+</jats:sup> and Mn<jats:sup>2+</jats:sup> concomitantly but has a much lower affinity for Mn<jats:sup>2+</jats:sup> (apparent <jats:italic>K</jats:italic><jats:sub>d</jats:sub> ~ 0.5 m<jats:sc>m</jats:sc>). Stoichiometries of transported ions per ATP hydrolysed, <jats:italic>V</jats:italic><jats:sub>max</jats:sub> values and activation energies are very similar. Altogether, Ca<jats:sup>2+</jats:sup>‐ATPase appears to use the same mechanism for transporting Mn<jats:sup>2+</jats:sup> as that for Ca<jats:sup>2+</jats:sup>.</jats:p>
Journal
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- FEBS Letters
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FEBS Letters 590 (14), 2086-2095, 2016-06-23
Wiley