钠-23核磁共振作为钠与肌钙蛋白C及胰蛋白酶片段结合的指标，与钙含量及伴随的构象变化的关系。

Sodium-23 nuclear magnetic resonance as an indicator of sodium binding to troponin C and tryptic fragments, in relation to calcium content and attendant conformational changes.

作者信息

Delville A, Grandjean J, Laszlo P, Gerday C, Grabarek Z, Drabikowski W

出版信息

Eur J Biochem. 1980 Apr;105(2):289-95. doi: 10.1111/j.1432-1033.1980.tb04500.x.

DOI:10.1111/j.1432-1033.1980.tb04500.x

Abstract

The relaxation rate enhancements of the 23Na nuclei for NaHCO3 solutions of troponin C and its tryptic peptides TR-1 and TR-2 indicate true binding of Na+ ions to these biomolecules. The low-affinity sites I and II of TR-1 and troponin C are the sites of competitive Na+/Ca2+ binding, below one calcium ion per molecule, with log KNa approximately 2. At low calcium content Na+ ions bind to TR-2 and to troponin C non-competitively with Ca2+ ions; binding of Ca2+ ions to the high-affinity sites III and IV allosterically affects the binding of the Na+ ions: even when sites I and II, located on TR-1 or sites I, II, III, IV of troponin C, are saturated with Ca2+ ions, Na+ ions continue to bind weakly at secondary binding sites.

摘要

肌钙蛋白C及其胰蛋白酶肽TR - 1和TR - 2的NaHCO₃溶液中²³Na核的弛豫速率增强表明Na⁺离子与这些生物分子发生了真实结合。TR - 1和肌钙蛋白C的低亲和力位点I和II是竞争性Na⁺/Ca²⁺结合位点，每个分子低于一个钙离子，log KNa约为2。在低钙含量时，Na⁺离子与TR - 2以及肌钙蛋白C与Ca²⁺离子非竞争性结合；Ca²⁺离子与高亲和力位点III和IV的结合会变构影响Na⁺离子的结合：即使位于TR - 1上的位点I和II或肌钙蛋白C的位点I、II、III、IV被Ca²⁺离子饱和，Na⁺离子仍会在二级结合位点微弱结合。