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.

CONTENTS

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.

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.

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 

Image Courtesy:

1.”Troponin Ribbon Diagram”By MetskasLA – Own work, (CC0) via Commons Wikimedia  
2.”Troponin-activation” (CC BY-SA 3.0) via Commons Wikimedia