Which of the following has ATP binding site?

Options

A. Light meromyosin
B. Troponin
C. Heavy meromyosin
D. Tropomyosin

Answer

To determine which of the following components has an ATP binding site, we need to analyze the options provided: light meromyosin, troponin, heavy meromyosin, and tropomyosin.

### Step-by-Step Solution:

1. **Understanding Myofibrils**:
- Myofibrils are the contractile units of muscle fibers and consist of two types of bands: dark bands (A bands) and light bands (I bands). The dark bands are primarily made of myosin, while the light bands are made of actin and associated proteins.

2. **Identifying Components**:
- **Light Meromyosin**: This is a part of the myosin molecule but does not contain the ATP binding site.
- **Troponin**: This is a regulatory protein that binds calcium ions and helps in muscle contraction but does not have an ATP binding site.
- **Heavy Meromyosin**: This portion of myosin contains the head region, which is responsible for binding ATP and interacting with actin during muscle contraction.
- **Tropomyosin**: This protein regulates the interaction between actin and myosin but does not have an ATP binding site.

3. **Conclusion**:
- Among the options given, **heavy meromyosin** is the only component that has an ATP binding site. The myosin head, which is part of heavy meromyosin, binds ATP, allowing for the muscle contraction mechanism.

### Final Answer:
The correct answer is **C) Heavy Meromyosin**.

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