[Effect of urea on conformational changes in the active site of native and reconstituted Ca-ATPase of the sarcoplasmic reticulum]
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Updated: Oct 3, 2026

Purification of the Sarco-Endoplasmic Reticulum Ca2+-ATPase from Rabbit Muscle
Published on: March 21, 2025
M G Vinokurov1, M N Ivkova, V A Pechatnikov
1Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia.
Abstract:
The effect of urea (1-3 M) on conformational changes in the active center of native and reconstituted Ca-ATPase of sarcoplasmic reticulum modified by fluorescein-5-isothiocyanate (FITC) was studied using the method of fluorescence titration by neodymium (Nd3+) ions. Based on the analysis of curves of fluorescence quenching of FITC-labeled Ca-ATPase by Nd3+ ions, the parameters characterizing the structural changes in the Mg-ATP binding center were determined. It was assumed that FITC and Nd3+ ion bind to different polypeptide fragments moving relative to each other, which provides the conformational lability of the nucleotide binding site at some stages of the catalytic cycle. A comparison of structural changes caused by urea at the active site of native and reconstituted Ca-ATPase of sarcoplasmic reticulum indicates that the Nd3+ binding center is localized in the region of contacts of monomers in the oligomer.
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