Question

In: Chemistry

An octapeptide with the amino acids < Ile, Arg, Met, Phe, Pro, Thr, Tyr, Val >...

An octapeptide with the amino acids < Ile, Arg, Met, Phe, Pro, Thr, Tyr, Val > was subjected to digestion reactions A, B and C in order to deduce its amino acid sequence. The following results were obtained. The exact position occupied by each of the amino acids (positions 1-8 in the sequence) will be known when the results are analyzed

A. Digestion with Trypsin yielded a [Thr-Arg] dipeptide and a [hexapeptide] with the remaining amino acids.

Question (A1): Explain the reasoning for the fragmentation pattern
Question (A2): What can you deduce regarding the exact positions occupied by Thr and Arg in the

sequence?

B. Cyanogen bromide treatment of the octapeptide also yielded a dipeptide [Phe-Pro] and a hexapeptide. Question (B1): Explain the reasoning for the above fragmentation pattern

Question (B2): What can you deduce regarding the exact positions occupied by Phe and Pro in the sequence?

C. Chymotrypsin cleaved the octapeptide into two tetrapeptides, one with and the other

Question (C1): Explain the reasoning for the above pattern
Question (C2): What can you deduce regarding the exact positions occupied by Val and Ile in the

sequence?

Question (D): What is the sequence of the peptide?

Expert Solution

Ans A1- Fragmentation pattern is based on the specific cleavge site of trypsin. Site for Trypsin cleavage is Arginine and Lysine.

Ans-A2- As per dipetide pattern Thr-Arg are first and second amino acid respectively in the octapetide frame as trypsin would cut the Arginine C terminus thereby separating it in two parts i.e. Thr-Arg and remaining Hexapeptide.

Ans B1- Cyanogen bromide hydrolyzes peptide bonds at the C-terminus of methionine residues. This reaction is used to reduce the size ofpolypeptide segments for identification and sequencing..CNBr will cut at the C terminus of Methionine hence hexapeptide and remaining two amino acids as Phe-Pro.

Ans-B2- Phe-Pro will be last two amino acids of the octa frame.

Ans C1- Chymotrypsin will cleave Carboxyl Side of Aryl Amino Acids e.g. Phe, Tyr & Trp

Ans C2- Val and Ile will be either side of of the Tyrosine as tyrosine will be in the mid of frame.

Ans C3- Thr-Arg-Val-Tyr-Ile-Met-Phe-Proline

queen_honey_blossom answered 1 month ago

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