Troponin I is a part of the troponin complex

Troponin complex

Troponin complex is a heteromeric protein playing an important role in the regulation of skeletal and cardiac muscle contraction. Troponin complex consists of three different subunits – troponin T , troponin I and troponin C . Each subunit is responsible for a part of troponin complex function...

. It binds to actin

Actin

Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...

 in thin myofilaments to hold the actin-tropomyosin complex in place. Because of it myosin cannot bind actin in relaxed muscle. When calcium binds to the Troponin C it causes conformational changes which lead to dislocation of troponin I and finally tropomyosin leaves the binding site for myosin on actin leading to contraction of muscle. The letter I is given due to its inhibitory character.

The tissue specific subtypes are:

• Slow-twitch skeletal muscle isoform troponin I, TNNI1
  TNNI1
  Troponin I, slow skeletal muscle is a protein that in humans is encoded by the TNNI1 gene.-Further reading:...
  
   (1q31.3)
• Fast-twitch skeletal muscle isoform troponin I, TNNI2
  TNNI2
  Troponin I, fast skeletal muscle is a protein that in humans is encoded by the TNNI2 gene.-Further reading:...
  
   (11p15.5)
• Cardiac troponin I, TNNI3
  TNNI3
  Troponin I, cardiac muscle is a protein that in humans is encoded by the TNNI3 gene.-Interactions:TNNI3 has been shown to interact with PKD2L1, Troponin C type 1 and Polycystic kidney disease 2.-Further reading:- External links :*...
  
   (19q13.4)

cTnI

Human troponin I is presented in cardiac muscle tissue by a single isoform with molecular weight 23876 Da and it consists of 209 amino acid residues. The theoretical pI of cTnI is 9.87. cTnI molecule contains two serines in the 22 and 23 positions. Both amino acid residues can be phosphorylated in vivo by protein kinase A, so four forms of protein – one dephospho, two monophospho and one bisphospho – can coexist in the cell. Phosphorylation of cTnI changes the conformation of the protein and modifies its interaction with other troponins as well as the interaction with anti-TnI antibodies. According to the latest findings significant part of cTnI released into the patient’s blood stream is phosphorylated . For more than 15 years cTnI has been known as a reliable marker of cardiac muscle tissue injury. It is considered to be more sensitive and significantly more specific in diagnosis of the myocardial infarction than the “golden marker” of last decades – CKMB, as well as myoglobin and LDH isoenzymes.

HyTest Ltd

HyTest Ltd

HyTest Ltd is a producer of monoclonal antibodies and antigens for the diagnostic industry and research communities all around the world. HyTest was established in 1994 and has become the global market leader in supplying certain reagents. HyTest is known for its investments in research and...

holds patents for ‘Method and kit for the diagnosis of troponin I’ (US7285418 and EP0938678).