Lanthanide binding to cardiac and skeletal muscle microsomes. Effects of adenosine triphosphate, cations, and ionophores

Norman Krasnow

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Lanthanide (gadolinium, Gd) binding to cardiac and skeletal muscle microsomes was studied, and high- and low-affinity sites were identified. The high-affinity constant was 106 M-1, and there were 131 and 107 nmol/mg bound to this site in dog heart and rabbit skeletal muscle, respectively. Zn2+, Cd2+, Al3+, and Ca2+ (5 mm) inhibited binding, especially of the high-affinity site. Ionophores X537A (10 μm) and A23187 (1-2 μm) increased lanthanide binding and did not cause release. Addition of ATP in low concentration (20-50 μm) increased the binding of Gd without hydrolysis of the ATP. The extra binding induced by ATP was blocked by heating the microsomes and was reversed by [ethylenebis(oxyethylenenitrilo)]tetraacetic acid. High concentrations (10-4-10-3, m) of ATP blocked extra Gd binding by competitive chelation. The Ca2+-activated ATPase was inhibited by Gd and stimulated by X537A. The Gd did not block the ionophore-stimulated increase in Ca2+-ATPase activity. It is postulated that lanthanides bind predominantly to the ionophoric component of the Ca-transport site rather than the hydrolytic site and that ATP may facilitate such binding without being split.

Original languageEnglish
Pages (from-to)322-330
Number of pages9
JournalArchives of Biochemistry and Biophysics
Volume181
Issue number1
DOIs
StatePublished - May 1977
Externally publishedYes

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