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Mn 2+ transport by Ca 2+ ‐ATPase of sarcoplasmic reticulum
Author(s) -
Yonekura ShinIchiro,
Toyoshima Chikashi
Publication year - 2016
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1002/1873-3468.12244
Subject(s) - endoplasmic reticulum , chemistry , atpase , vesicle , atp hydrolysis , calcium , ion transporter , biophysics , calcium atpase , membrane transport , enzyme , biochemistry , membrane , biology , organic chemistry
Ca 2+ ‐ATPase of sarcoplasmic reticulum is known to pump Mn 2+ in addition to Ca 2+ , but whether its transport mechanism is identical to that of Ca 2+ is ambiguous. To clarify, we examined, by atomic absorption spectroscopy, competition between Mn 2+ and Ca 2+ in active transport using vesicles of sarcoplasmic reticulum (SR). Here, we demonstrate that Ca 2+ ‐ATPase transports Ca 2+ and Mn 2+ concomitantly but has a much lower affinity for Mn 2+ (apparent K d ~ 0.5 m m ). Stoichiometries of transported ions per ATP hydrolysed, V max values and activation energies are very similar. Altogether, Ca 2+ ‐ATPase appears to use the same mechanism for transporting Mn 2+ as that for Ca 2+ .