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Sarcoplasmic reticulum calcium ATP
Author(s) -
Coan Carol,
Jakobs Pia,
Ji Ji-Ying,
Murphy Alexander J.
Publication year - 1993
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 - 10.1016/0014-5793(93)80433-u
Subject(s) - endoplasmic reticulum , chemistry , carbodiimide , calcium , enzyme , phosphorylation , atp hydrolysis , atpase , calcium atpase , biophysics , biochemistry , incubation , stereochemistry , biology , organic chemistry
The sarcoplasmic reticulum Ca 2+ ‐ATPase loses hydrolytic activity and the ability to be phosphorylated by P i 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. Mg 2+ protects against loss of activity and tempamine labeling with a mid‐point of about 3 mM in the absence of Ca 2+ . This is similar to the K d for a Mg 2+ that serves as a cofactor in enzyme phosphorylation. The Mg 2+ protection constant is lowered by an order of magnitude when Ca 2+ is bound to the transport sites. It is suggested that control of the Mg 2+ binding site affinity may be part of the mechanism of enzyme activation by Ca 2+ .