Sarcoplasmic reticulum calcium ATP
- 14 November 1993
- journal article
- Published by Wiley in FEBS Letters
- Vol. 335 (1) , 33-36
- https://doi.org/10.1016/0014-5793(93)80433-u
Abstract
The sarcoplasmic reticulum Ca2+-ATPase loses hydrolytic activity and the ability to be phosphorylated by Pi following incubation with EDC [1-ethyl-3-(3-dimethylaminopropyl)carbodiimide]. 4 nmol of tempamine per mg SR protein can be coupled to either a glu or an asp side chain through the EDC reaction. Mg2+ protects against loss of activity and tempamine labeling with a mid-point of about 3 mM in the absence of Ca2+. This is similar to the Kd for a Mg2+ that serves as a cofactor in enzyme phosphorylation. The Mg2+ protection constant is lowered by an order of magnitude when Ca2+ is bound to the transport sites. It is suggested that control of the Mg2+ binding site affinity may be part of the mechanism of enzyme activation by Ca2+Keywords
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