This study clarifies the structural interactions of bisphosphorylated cardiac troponin I, showing it interacts with cTnT and/or cTnI rather than cTnC.
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Refines troponin interaction models in cardiac muscle; leaves open translation to human contractility or therapy.
Cardiac troponin I, the inhibitory subunit of the heterotrimeric cardiac troponin (cTn) complex is phosphorylated by protein kinase A at two serine residues located in its heart-specific N-terminal extension. This flexible arm interacts at different sites within cTn dependent on its phosphorylation degree. Bisphosphorylation is known to induce conformational changes within cTnI which finally lead to a reduction of the calcium affinity of cTnC. However, as we show here, the bisphosphorylated cTnI arm does not interact with cTnC, but with cTnT and/or cTnI.
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Schmidtmann et al. (2002) studied this question.
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