A protein biochemist attempted to determine the amino acid sequence of a decapep

Question

A protein biochemist attempted to determine the amino acid sequence of a decapeptide. Use the results from the trypsin, chymotrypsin, and cyanogen bromide treatments to suggest the amino acid sequence of this decapeptide. Trypsin digestion gave two fragments, containing the following residues (not in order; 1: Ala, Arg, Phe, Pro, Thr, Trp, Tyr T2: Lys, Met, Val Chmidno pgave thre fragments with the following residues (not in orderk 1: Ala, Arg, Phe, Pro CT2: Thr, Trp CT3: Lys, Met, Tyr, Val N-terminal analysis of the CT1 tetrapeptide indicated that the N-terminal amino acid was Ala. The cyanogen bromide gave only one single amino acid, methionine, and a nonapeptide. What is a possible sequence of the decapeptide? Use three-letter abbreviations in your answer, and add dashes between residues. Met- val-lys-tyr-thr trp- ala- arg- pro- phe

Explanation / Answer

Ans) Cyanogen Bromide (CNBr ) cleave the peptide at the carboxyl side of the methionine amino acid.

Trypsin cleave a peptide at the carboxyl side of RN-1 = Arg, Lys amino acidbut cannot cleave if Prolone is present at Rn = Proline

Chymotypsin cleave a peptide at the carboxyl side of RN-1= Phe, Trp, Tyr. but cannot cleave if Proline is present at Rn = Proline

The sequence will be Met- Val- Lys - Tyr - Thr-Trp- Ala-Phe-Pro-Arg

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