A sample of an unknown peptide undergoes a single round of Edman degradation, wh

Question

A sample of an unknown peptide undergoes a single round of Edman degradation, which liberates ATZ-Gly. Another sample of the peptide is treated with trypsin, and a third sample is treated with chymotrypsin. The table below shows the fragments.

Tryptic fragments:

Phe-Ser

Gly-Val-Tyr-Arg

Asn-Tyr-Ala-Pro-Thr-Cys-Val-Gln-Lys

Chymotryptic fragments:

Arg-Asn-Tyr

Ala-Pro-Thr-Cys-Val-Gln-Lys-Phe

Ser

Gly-Val-Tyr

A) line up the fragments so that the fragments with the same sequences overlap.

B) Write the sequence of the peptide

Explanation / Answer

Edman degradation removes amino acid fron N-terminal,

so, as Gly is liberated during Edman degradation, it means Gly is at the N- terminal

A)

Tryptic fragments: will be lines up as

Gly-Val-Tyr-Arg ---Asn-Tyr-Ala-Pro-Thr-Cys-Val-Gln-Lys ---- Phe-Ser

Chymotryptic fragments: will be lined up as

Gly-Val-Tyr --- Arg-Asn-Tyr ---- Ala-Pro-Thr-Cys-Val-Gln-Lys-Phe --- Ser

B)

sequence of the peptide is

Gly-Val-Tyr-Arg -Asn-Tyr-Ala-Pro-Thr-Cys-Val-Gln-Lys- Phe-Ser

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