AI Article Synopsis
- - The study focuses on understanding how muscles experience activation through mechanical stretch by examining the structure of calcium-loaded troponin C (TnC) from Lethocerus and its interaction with troponin I (TnI).
- - It was found that only one calcium ion is needed to change the shape of TnC, allowing it to interact differently with TnI compared to vertebrate muscles.
- - The research also indicates that the N lobe of TnC does not participate in TnI interactions, suggesting it does not play a regulatory role, providing new insights into how muscles contract when stretched.
Article Abstract
To gain a molecular description of how muscles can be activated by mechanical stretch, we have solved the structure of the calcium-loaded F1 isoform of troponin C (TnC) from Lethocerus and characterized its interactions with troponin I (TnI). We show that the presence of only one calcium cation in the fourth EF hand motif is sufficient to induce an open conformation in the C-terminal lobe of F1 TnC, in contrast with what is observed in vertebrate muscle. This lobe interacts in a calcium-independent way both with the N terminus of TnI and, with lower affinity, with a region of TnI equivalent to the switch and inhibitory peptides of vertebrate muscles. Using both synthetic peptides and recombinant proteins, we show that the N lobe of F1 TnC is not engaged in interactions with TnI, excluding a regulatory role of this domain. These findings provide insights into mechanically stimulated muscle contraction.
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| http://dx.doi.org/10.1016/j.str.2007.05.007 | DOI Listing |
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