TY - JOUR
T1 - Lanthanide binding to cardiac and skeletal muscle microsomes. Effects of adenosine triphosphate, cations, and ionophores
AU - Krasnow, Norman
N1 - Funding Information:
1 Supported, in part, by Grant the United States Public Health Institutes of Health, Bethesda,
PY - 1977/5
Y1 - 1977/5
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0017647892&partnerID=8YFLogxK
U2 - 10.1016/0003-9861(77)90511-2
DO - 10.1016/0003-9861(77)90511-2
M3 - Article
C2 - 141909
AN - SCOPUS:0017647892
SN - 0003-9861
VL - 181
SP - 322
EP - 330
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -