The first amino acid in any polypeptide chain of prokaryote is always

Options

A. Formylated methionine
B. Formylated arginine
C. Lysine
D. Methionine

Answer

To answer the question regarding the first amino acid in any polypeptide chain of prokaryotes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Polypeptide Chains**:
- Polypeptides are chains of amino acids that make up proteins. The sequence of amino acids in a polypeptide is determined by the genetic code.

2. **Identifying the Start Codon**:
- In both prokaryotes and eukaryotes, the synthesis of proteins begins at a specific codon on the mRNA. This codon is known as the start codon.

3. **Start Codon in Prokaryotes**:
- The start codon for protein synthesis is typically AUG, which codes for the amino acid methionine.

4. **Formylated Methionine in Prokaryotes**:
- In prokaryotes, the first amino acid incorporated into the polypeptide chain is not just methionine, but a modified form known as N-formylmethionine (fMet). This modification is specific to prokaryotic organisms.

5. **Conclusion**:
- Therefore, the first amino acid in any polypeptide chain of prokaryotes is always N-formylmethionine (fMet).

### Final Answer:
The first amino acid in any polypeptide chain of prokaryotes is always **N-formylmethionine (fMet)**.

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