What is the Difference Between Troponin I and Troponin T

The key difference between troponin I and troponin T is that the troponin I binds with actin while the troponin T binds with tropomyosin during muscle contractions.

Troponins are important protein molecules involve in muscle contraction. Studies on troponin are widely increasing due to its main importance as a cardiac marker in ischemic heart diseases. In human physiology, there are three types of troponins. The three separate genes code for these three types of troponins; Troponin C, Troponin T and Troponin I. The troponin I and Troponin T use as cardiac markers in the prognostics. Hence, Troponin I binds to the actin filaments during muscle contractions to hold the actin-tropomyosin complex in place. On the other hand, Troponin T binds to the tropomyosin during muscle contractions. Troponin T helps tropomyosin to rest on actin. Therefore, the key difference between Troponin I and Troponin T is the substrate to which they bind during muscle contractions.

1. Overview and Key Difference
2. What is Troponin I
3. What is Troponin T
4. Similarities Between Troponin I and Troponin T
5. Side by Side Comparison – Troponin I vs Troponin T in Tabular Form
6. Summary

What is Troponin I?

Troponin I is present in both cardiac and skeletal muscles. It is important in the process of muscle contraction. As it is present in the cardiac muscle, it has a value as a cardiac marker as well. Troponin I is a part of the muscle contraction apparatus. This protein is about 24kDa in weight. The main function of troponin I is to aid the formation of the actin-tropomyosin complex. Troponin I binds to the actin molecules to hold the actin-tropomyosin complex in place. The binding of the troponin I to the actin protein result in a conformational change in the protein. This prevents the binding of myosin in the relaxed muscle.

Difference Between Troponin I and Troponin T_Fig 01

Figure 01: Troponin

Troponin I can be further categorized based on the distribution of the troponin I. Thus, troponin I can be skeletal muscle-specific troponin I or cardiac Troponin I. Separate genes code for each of the troponins. Therefore, the identification of different troponin levels is possible. The most widely studied troponin I type is the Cardiac Troponin I. This is due to the vital role it plays as a cardiac marker during ischemic heart disease conditions. The cardiac troponin I levels are important in diagnosing myocardial infarction. During infarction, the cardiac troponin I levels go high.

What is Troponin T?

Troponin T is also a protein present in both skeletal and cardiac muscles. Similar to troponin I, Troponin T also aids in muscle contraction. Thus, the primary function of troponin T is to bind to the tropomyosin protein and help in the contraction process. The binding of troponin T to tropomyosin cause a conformational change which facilitates the binding of tropomyosin to actin. This initiates the muscle contraction process.

Difference Between Troponin I and Troponin T_Fig 02

Figure 02: Troponin Activation

Troponin T protein is also subcategorized based on their distribution. Troponin T is mainly of two types, the skeletal troponin T and the cardiac troponin T. Cardiac troponin T is a widely used cardiac marker for myocardial infarction. The level of cardiac troponin T increases during cardiac conditions. This makes Troponin T a good cardiac marker.

What are the Similarities Between Troponin I and Troponin T?

Both troponin I and T are proteins.
They involve in muscle contractions.
Also, they both are present in skeletal muscles as well as in cardiac muscles.
Furthermore, they are good as cardiac markers for myocardial infarction.
Besies, both, troponin I and T, have different genes coding for the protein.

What is the Difference Between Troponin I and Troponin T?

Troponins are of three types. Among them, troponin I and troponin T are two protein types present as cardiac and skeletal muscles. They are involved in muscle contraction. The key difference between troponin I and troponin T is the substrate which they bind. Troponin I binds with the actin filaments during muscle contractions while troponin T binds to the tropomyosin during muscle contractions.

The below infographic tabulates the difference between troponin I and troponin T as a side by side comparison.

Summary – Troponin I vs Troponin T

Troponin I and Troponin T are two common cardiac markers. In physiology, troponin I and T are present in both skeletal and cardiac muscles. They have a main role in the muscle contraction process. Troponin I binds to the thin actin proteins and helps in maintaining the structure of the actin-tropomyosin complex. In contrast, troponin T binds to tropomyosin and facilitates the binding to the actin protein during muscle contractions. Both troponin I and T levels go up during cardiac conditions. Hence, this is the difference between troponin I and troponin T.

Reference:

1.Roppolo, L P, et al. “A Comparison of Troponin T and Troponin I as Predictors of Cardiac Events in Patients Undergoing Chronic Dialysis at a Veteran’s Hospital: a Pilot Study.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, Aug. 1999. Available here