Ca2+, Mg2+-ATPase of Microsomal Membranes from Bovine Aortic Smooth Muscle: Effects of Sr2+ and Cd2+ on Ca2+ Uptake and Formation of the Phosphorylated Intermediate of the Ca2+, Mg2+-ATPase1
- 1 March 1986
- journal article
- research article
- Published by Oxford University Press (OUP) in The Journal of Biochemistry
- Vol. 100 (3) , 765-772
- https://doi.org/10.1093/oxfordjournals.jbchem.a121769
Abstract
The effects of various divalent cations on the Ca 2+ uptake by microsomes from bovine aortic smooth muscle were studied. High concentrations (1 mM) of Co 2+ , Zn 2+ , Mn 2+ , Fe 2+ , and Ni 2+ inhibited neither the Ca 2+ uptake by the microsomes nor the formation of the phosphorylated intermediate (E ∼ P) of the Ca 2+ , Mg 2+ -ATPase of the microsomes. The cadmium ion, however, inhibited both the Ca 2+ uptake and the E∼P formation by the microsomes. Dixon plot analysis indicated that Cd 2+ inhibited ( K1 = 135 µM) the Ca 2+ dependent E∼P formation in a non-competitive manner. The inhibitory effect of Cd 2+ was lessened by cysteine or dithiothreitol. The strontium ion inhibited the Ca 2+ uptake competitively, while the E∼P formation increased on the addition of Sr 2+ at low Ca 2+ concentrations. At a low Ca 2+ concentration (1 µM), Sr 2+ was taken up by the aortic microsomes in the presence of 1 mM ATP. It is thus suggested that Sr 2+ replaces Ca 2+ at the Ca 2+ binding site on the ATPase.This publication has 1 reference indexed in Scilit:
- Characterization of the (Ca2+-Mg2+)ATPase Purified by Calmodulin-Affinity Chromatography from Bovine Aortic Smooth Muscle1The Journal of Biochemistry, 1984