A tetradecapeptide (14 amino acid residues) gives the following peptide fragments on partial hydrolysis. From this information, deduce the primary structure of this polypeptide. Fragments are grouped according to size. $$ \begin{array}{ll} \hline \text { Pentapeptide Fragments } & \text { Tetrapeptide Fragments } \\ \hline \text { Phe-Val-Asn-Gln-His } & \text { Gln-His-Leu-Gys } \\ \text { His-Leu-Cys-Gly-Ser } & \text { His-Leu-Val-Glu } \\ \text { Gly-Ser-His-Leu-Val } & \text { Leu-Val-Glu-Ala } \\ \hline \end{array} $$

Short Answer

Expert verified
Answer: The primary structure of the given polypeptide is Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-Val-Glu-Ala.

Step by step solution

01

Identify Overlapping Fragments

First, let's look for overlapping sequences among the fragments. We do not yet know if the fragments should be read from left to right or from right to left, so we will consider both possibilities for now.
02

Overlapping the Pentapeptide Fragments

Let's start with the pentapeptide fragments: 1. Phe-Val-Asn-Gln-His 2. His-Leu-Cys-Gly-Ser 3. Gly-Ser-His-Leu-Val Consider fragment 1 and 2: - Phe-Val-Asn-Gln-His overlaps with His-Leu-Cys-Gly-Ser by 1 amino acid (His). Now consider fragment 1 and 3: - Phe-Val-Asn-Gln-His has no overlap with Gly-Ser-His-Leu-Val. Finally, consider fragment 2 and 3: - His-Leu-Cys-Gly-Ser overlaps with Gly-Ser-His-Leu-Val by 4 amino acids (Gly-Ser-His-Leu). Knowing these overlaps, we can combine fragments 1, 2, and 3: - Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-Val
03

Overlapping the Tetrapeptide Fragments

Now let's analyze the tetrapeptide fragments: 1. Gln-His-Leu-Gys 2. His-Leu-Val-Glu 3. Leu-Val-Glu-Ala Consider fragment 1 and 2: - Gln-His-Leu-Gys has no overlap with His-Leu-Val-Glu. Now consider fragment 1 and 3: - Gln-His-Leu-Gys has no overlap with Leu-Val-Glu-Ala. Finally, consider fragment 2 and 3: - His-Leu-Val-Glu overlaps with Leu-Val-Glu-Ala by 3 amino acids (Leu-Val-Glu). We can combine fragments 2 and 3: - His-Leu-Val-Glu-Ala
04

Combining Pentapeptide and Tetrapeptide Sequences

Now let's combine the pentapeptide overlapping sequence (Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-Val) with the tetrapeptide overlapping sequence (His-Leu-Val-Glu-Ala). We can see that the combined pentapeptide sequence already has a His-Leu-Val segment, which can overlap with the His-Leu-Val segment in the tetrapeptide sequence. So, combining them, we obtain the final sequence: Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-Val-Glu-Ala
05

Final Sequence of the Polypeptide

The primary structure of the polypeptide, deduced from the given peptide fragments, is: Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-Val-Glu-Ala This sequence contains 14 amino acid residues, as required for a tetradecapeptide.

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