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Direct Observation of Ca2+-Induced Calmodulin Conformational Transitions in

IntactXenopus laevis Oocytes by 19F NMR Spectroscopy

In-cell nuclear magnetic resonance (NMR) spectroscopy, as a front research field of NMR spectroscopy in recent years, provides atomic resolution information about protein structure, dynamics and interactions in living cells.  

In a recent study,  Prof. Conggang LI’s research group from Wuhan Institute of Physics and Mathematics,  Chinese Academy of Sciences,  have for the first time directly observed the CaM (calmodulin) conformational transition in intact Xenopus laevis oocytes by using 19F NMR. In living cells,, most CaM is in the apo-form (Ca2+-free form), and Ca-CaM (Ca2+-bound CaM) form only appears at high Ca2+ levels. The affinity of Ca2+ for CaM is enhanced by MLCK (Myosin Light Chain Kinase) in cells, suggesting that MLCK can be activated at lower Ca2+ concentration, resulting in further signal transduction. Their observations support the idea that signaling-pathway activation is regulated by the relative binding affinity of CaM targets at different Ca2+ concentrations. Further they tried the world's first 19F PCS (Pseudocontact Shifts) experiments of proteins inside cells, and concluded that in-cell 19F PCS can yield long range structural constraints. They believed the 19F method demonstrated here with CaM can be applied to other cellular transduction systems in living cells. 

This work  entitled Direct Observation of Ca2+-Induced Calmodulin Conformational Transitions in IntactXenopus laevis Oocytes by 19F NMR Spectroscopy has been published as a Very Important Paper (VIP) in Angewandte Chemie International Edition (DOI: 10.1002/anie.201500261).  

This work was supported by the Ministry of Science and Technology of China (grant 2013CB910200), the 1000 Young Talents Program, and National Natural Sciences Foundation of China (grants 21173258, 21120102038, and 21221064). 

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