In lac operon, a helper protein that binds to the promotor and facilitaties attachment of RNA polymerase and accelerates the rate of transcription. This protein is called

Options

A. Catabolite activator protein
B. Inactive repressor protein
C. Essential metabolic protein
D. Amino acid activating enzyme

Answer

**Step-by-Step Solution:**

1. **Understanding the lac operon**: The lac operon is a well-studied model in molecular biology that regulates the metabolism of lactose in bacteria, particularly E. coli. It consists of genes that are involved in the transport and breakdown of lactose.

2. **Identifying the role of helper proteins**: In the context of the lac operon, certain proteins help facilitate the transcription of genes. These proteins can bind to specific regions of the DNA, such as the promoter, to assist in the process of transcription.

3. **Recognizing the function of the specific protein**: The question specifies a helper protein that binds to the promoter, facilitates the attachment of RNA polymerase, and accelerates transcription. This indicates that we are looking for a protein that enhances the transcription process.

4. **Evaluating the options**:
- **Option 1: Catabolite Activator Protein (CAP)** - This protein binds to the promoter region of the lac operon when glucose levels are low, facilitating the binding of RNA polymerase and thus increasing the rate of transcription.
- **Option 2: Inactive Repressor Protein** - This protein does not facilitate transcription; instead, it inhibits it unless it binds to a co-repressor.
- **Option 3: Essential Metabolic Protein** - This term does not specifically refer to a protein involved in transcription regulation.
- **Option 4: Amino Acid Activating Enzyme** - This enzyme is involved in the process of attaching amino acids to tRNA, not in transcription.

5. **Conclusion**: Based on the functions described, the correct answer is **Catabolite Activator Protein (CAP)**, as it is the helper protein that binds to the promoter, facilitates RNA polymerase attachment, and accelerates transcription in the lac operon.

**Final Answer**: Catabolite Activator Protein (CAP)

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