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Surface model of the skeletal (red) troponin (subunits T purple, I cyan, C green), according to PDB 1YV0

The troponins are three protein complexes that occur in the skeletal and heart muscles of the chordates . They each have three subunits, with subunit C being responsible for binding calcium , T for binding tropomyosin and I for binding actin (I for inhibitory ). Together with myosin and actin , these protein complexes form the mobile (contractile) part of the muscles .

Biological function

If calcium ions bind to troponin C, the complex changes its conformation and thus releases the myosin binding sites, which enables contraction. Troponin C is largely homologous with calmodulin , which is mainly responsible for binding calcium ions in the cells of the smooth muscles.


There are three troponins, which are made up of a total of eight different subunits, whereby the two known TN-C subunits differ only slightly:


Changes in the genes that code for one of the troponin subunits can lead to hereditary diseases:


  • Jeremy M. Berg, John L. Tymoczko, Lubert Stryer : Biochemistry. 6 edition, Spektrum Akademischer Verlag, Heidelberg 2007. ISBN 978-3-8274-1800-5 .
  • Donald Voet, Judith G. Voet: Biochemistry. 3rd edition, John Wiley & Sons, New York 2004. ISBN 0-471-19350-X .
  • Bruce Alberts , Alexander Johnson, Peter Walter, Julian Lewis, Martin Raff, Keith Roberts: Molecular Biology of the Cell , 5th Edition, Taylor & Francis 2007, ISBN 978-0815341062 .