Which of the following is not the part of Heavy Meromyosin (HMM) ?

Options

A. Globular head
B. Short arm
C. Binding site for actin
D. Binding site for Tropomyosin

Answer

To solve the question "Which of the following is not a part of Heavy Meromyosin (HMM)?", we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Heavy Meromyosin (HMM)**:
- Heavy Meromyosin is a part of the myosin filament found in striated muscles.
- It consists of heavy chains and light chains, with two heavy chains and four light chains present in the meromyosin.

2. **Identifying Components of HMM**:
- HMM contains several structural components:
- **Globular Head**: This is a prominent feature of HMM, responsible for binding to actin during muscle contraction.
- **Short Arm**: This is also a part of the HMM structure, which connects the globular head to the rest of the myosin filament.
- **Binding Site for Actin**: HMM has a binding site for actin, which is crucial for muscle contraction.
- **Binding Site for Tropomyosin**: Tropomyosin is a regulatory protein that binds to actin, but it is not a part of HMM itself.

3. **Analyzing the Options**:
- **Option 1: Globular Head** - Part of HMM (Correct).
- **Option 2: Short Arm** - Part of HMM (Correct).
- **Option 3: Binding Site for Actin** - Part of HMM (Correct).
- **Option 4: Binding Site for Tropomyosin** - Not part of HMM (Incorrect).

4. **Conclusion**:
- The only option that is not part of Heavy Meromyosin is **Binding Site for Tropomyosin**.

### Final Answer:
**Binding Site for Tropomyosin** is not a part of Heavy Meromyosin (HMM).

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