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Chapter 21: Q66P (page 1028)

Treatment of a polypeptide with 2-mercaptoethanol yields two polypeptides with the following primary structures:

Val-Met-Tyr-Ala-Cys-Ser-Phe-Ala-Glu-Ser

Ser-Cys-Phe-Lys-Cys-Trp-Lys-Tyr-Cys-Phe-Arg-Cys-Ser

Treatment of the original intact polypeptide with chymotrypsin yields the following peptides:

1. Ala, Glu, Ser 3. Tyr, Val, Met 5. Ser, Phe, 2 Cys, Lys, Ala, Trp

2. 2 Phe, 2 Cys, Ser 4. Arg, Ser, Cys 6. Tyr, Lys

Determine the positions of the disulfide bridges in the original polypeptide.

Short Answer

Expert verified

The position of the disulfide bridges in the original polypeptide is given above.

Step by step solution

01

Peptide bond

Peptide bonds are created by linking the carboxyl group of one amino acid with the amino group.

These bonds are generated by dehydration synthesis, which is called a condensation reaction between amino acids. Water molecules are released during the creation of this bond.

02

Determining the position of the disulfide bridges in the original polypeptide

2-mercaptoethanol cleaves the disulfide (-S-S-) bonds of the peptides in a polypeptide.

Chrymotrypsin cleaves the C-side peptide bond of aromatizering chains such as Phe, Tyr ad Trp.

The treatment with chymotrypsin produces six peptides for the polypeptide.

From fragments 2 and 5, it is confirmed that the former fragment is connected.

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Most popular questions from this chapter

What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step?

(a)

(b) CH3SCH2CH2Br

Reaction of a polypeptide with carboxypeptidase A releases Met. The polypeptide undergoes partial hydrolysis to give the following peptides.

What is the sequence of the polypeptide?

1. Ser, Lys, Trp4. Leu, Glu, Ser 7. Glu, His 10. Glu, His, Val

2. Gly, His, Ala 5. Met, Ala, Gly8. Leu, Lys, Trp11. Trp, Leu, Glu

3. Glu, Val, Ser 6. Ser, Lys, Val 9. Lys, Ser 12. Ala, Met

Glutathione is a tripeptide whose function is to destroy harmful oxidizing agents in the body. Oxidizing agents are bought to be responsible for some of the effects of aging and to play a causative role in cancer.

Glutathione removes oxidizing agents by reducing them. In the process, glutathione is oxidized, resulting in the formation of a disulphide bond between two glutathione molecules. An enzyme subsequently reduces the disulphide bond, returning glutathione to its original condition so it can react with another oxidizing agent.

a. What amino acids make up glutathione?

b. What is unusual about glutathione’s structure?

a. Calculate the overall yield of bradykinin when the yield for the addition of each amino acid to the chain is 70%.

b. What would be the overall yield of a peptide containing 15 amino acids if the yield for the incorporation of each is 80%?

Identify the location and type of charge on the hexapeptide Lys-Ser-Asp-Cys-His-Tyr at each of the following pH values:

a. pH = 1 b. pH = 5 c. pH = 7 d. pH = 12
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