Peptides and Amino Acids

The following fragments were isolated from a sample containing an octapeptide (i.e. a peptide containing eight amino acid residues). The first amino acid is Pro.

Pro-Gly-Ser Gln-Asp-Ser Asp-Ser-Gly-Pro Ser-Gln-Asp

Using the list below, enter the letters corresponding to the sequence of the original peptide.


A) Gly F) Leu K) Asn P) His
B) Pro G) Trp L) Cys Q) Glu
C) Ala H) Ile M) Gln R) Lys
D) Val I) Met N) Thr S) Tyr
E) Phe J) Ser O) Asp T) Arg

Enter a combination of 8 letters, in order, which give the name.

This is essentially a logic problem. Let's lay out the fragments like this:

1. Pro-Gly-Ser
2. Gln-Asp-Ser
3. Asp-Ser-Gly-Pro
4. Ser-Gln-Asp

Fragments 1 and 3 both begin or end with Pro, so let's flip around 3 so they both begin with Pro:

1. Pro-Gly-Ser
2. Gln-Asp-Ser
3. Pro-Gly-Ser-Asp
4. Ser-Gln-Asp

We can see that the beginning of the octapeptide is Pro-Gly-Ser-Asp.
Note that Ser is attached to Asp, just like in fragment 2. Let's flip it so it looks like 3.

1. Pro-Gly-Ser
2. Ser-Asp-Gln
3. Pro-Gly-Ser-Asp
4. Ser-Gln-Asp

From this, we can assume that the Asp at the end of 3 attaches to Gln. So our peptide now looks like this: Pro-Gly-Ser-Asp-Gln
Now in fragment 4, Asp attaches to Gln just like in our polypeptide. Let's flip it so it matches up.

Peptide: Pro-Gly-Ser-Asp-Gln

1. Pro-Gly-Ser
2. Ser-Asp-Gln
3. Pro-Gly-Ser-Asp
4. Asp-Gln-Ser

We can assume that Ser attaches to Gln on our peptide just like it does on fragment 4:
Pro-Gly-Ser-Asp-Gln-Ser
From this, we can assume that Gly-Pro attaches to Ser like in fragment 1. Let's flip it to see.

Peptide: Pro-Gly-Ser-Asp-Gln-Ser

1. Ser-Gly-Pro
2. Ser-Asp-Gln
3. Pro-Gly-Ser-Asp
4. Asp-Gln-Ser

So now we add fragment 1 to the end of our peptide: Pro-Gly-Ser-Asp-Gln-Ser-Gly-Pro
Now we have 8 amino acids in a polypeptide, so your answer is:

Pro-Gly-Ser-Asp-Gln-Ser-Gly-Pro (BAJOMJAB)

OR

Pro-Gly-Ser-Gln-Asp-Ser-Gly-Pro (BAJMOJAB)