Question

On complete hydrolysis, a polypeptide gives two alanine, one leucine, one methionine, one phenylalanine, and one valine residue. Partial hydrolysis gives the following fragments: Ala-Phe, Leu-Met, Val-Ala, Phe-Leu. It is known that the first amino acid in the sequence is valine and the last one is methionine. What is the complete sequence of amino acids?

Short answer

Answer: The complete amino acid sequence of the polypeptide is Val-Ala-Phe-Leu-Met.

Step-by-step solution

Identify the partial hydrolysis fragments

The partial hydrolysis fragments are Ala-Phe, Leu-Met, Val-Ala, and Phe-Leu.

Determine the sequence of fragments

From the fragments, we can see the following sequences: 1. Valine is the first amino acid, so Val-Ala should be at the beginning. 2. Methionine is the last amino acid, so Leu-Met should be at the end. 3. The fragment between Val-Ala and Leu-Met should connect them. We can see that the fragment Ala-Phe can connect Val-Ala and Phe-Leu (which in turn, connects with Leu-Met). The sequence of three fragments is: Val-Ala -> Ala-Phe -> Phe-Leu -> Leu-Met

Combine the sequence

Combining the fragments results in the complete sequence: Val-Ala-Ala-Phe-Phe-Leu-Leu-Met. Since we have two alanine, one leucine, one methionine, one phenylalanine, and one valine residue as mentioned in the problem, the actual final sequence would be without the duplications. So, the final sequence would be: Val-Ala-Phe-Leu-Met