Troponin complexes consist of three subunits - troponin T (also known as TnT or TNNT), troponin I (TnI or TNNI) and troponin C (TnC or TNNC). Troponin is therefore heterotrimeric, with each of the different subunits providing specific binding sites, allowing each troponin to interract with a single molecule of tropomyosin, an actin filament and a Ca²⁺ ion respectfully. The ability of troponin to bind Ca²⁺ allows it to undergo a conformational and therefore moves the tropomyosin away from the myosin binding site on actin. This means that the two filaments can form a cross bridge ^[1].

Troponin is thought to be specialised form another calcium ion binding protein, calmodulin, which is found in smooth muscle. The extra subunits, T and I, mean that the myofibrils are able to move towards the actin filaments very quickly for rapid contraction, This is needed in skeletal muscle for example.^[2]

References

↑ Molecular Biology of the Cell, 4th editionfckLRBruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter. 2002.
↑ Alberts, B. et al (2008) Molecular Biology of the Cell, 5th ed, Garland Science Taylor and Francis Group, New York, pp. 1028-1030

[1] Molecular Biology of the Cell, 4th editionfckLRBruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter. 2002.

[2] Alberts, B. et al (2008) Molecular Biology of the Cell, 5th ed, Garland Science Taylor and Francis Group, New York, pp. 1028-1030

[1]

[2]

Troponin

References

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