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PLoS One. 2012;7(11):e49013. doi: 10.1371/journal.pone.0049013. Epub 2012 Nov 7.

The Ca(2+) influence on calmodulin unfolding pathway: a steered molecular dynamics simulation study.

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  • 1Laboratory of Non-Coding RNAs, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.


The force-induced unfolding of calmodulin (CaM) was investigated at atomistic details with steered molecular dynamics. The two isolated CaM domains as well as the full-length CaM were simulated in N-C-terminal pulling scheme, and the isolated N-lobe of CaM was studied specially in two other pulling schemes to test the effect of pulling direction and compare with relevant experiments. Both Ca(2+)-loaded CaM and Ca(2+)-free CaM were considered in order to define the Ca(2+) influence to the CaM unfolding. The results reveal that the Ca(2+) significantly affects the stability and unfolding behaviors of both the isolated CaM domains and the full-length CaM. In Ca(2+)-loaded CaM, N-terminal domain unfolds in priori to the C-terminal domain. But in Ca(2+)-free CaM, the unfolding order changes, and C-terminal domain unfolds first. The force-extension curves of CaM unfolding indicate that the major unfolding barrier comes from conquering the interaction of two EF-hand motifs in both N- and C- terminal domains. Our results provide the atomistic-level insights in the force-induced CaM unfolding and explain the observation in recent AFM experiments.

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