The Structure of Lethocerus Troponin C: Insights into the Mechanism of Stretch Activation in Muscles

Gianfelice De Nicola, Christoph Burkart, Feng Qiu, Bogos Agianian, Siegfried Labeit, Stephen Martin, Belinda Bullard, Annalisa Pastore

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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.

Original languageEnglish (US)
Pages (from-to)813-824
Number of pages12
Issue number7
Publication statusPublished - Jul 18 2007




ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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