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Amino acid analysis of an octapeptide revealed the following composition:

2 Arg 1 Gly 1 Met 1 Trp 1 Tyr 1 Phe 1 Lys

The following facts were observed:

a. Edman degradation gave

(I couldnt get the image to upload because it was a chemical structure from word but I determined the N-terminal has a GLY)

b. CNBr treatment yielded a pentapeptide and a tripeptide containing phenylalanine.

c. Chymotrypsin treatment yielded a tetrapeptide containing a C-terminal indole amino acid and two dipeptides.

d. Trypsin treatment yielded a tetrapeptide, a dipeptide, and free Lys and Phe.

e. Clostripain yielded a pentapeptide, a dipeptide, and free Phe.

What is the amino acid sequence of this octapeptide?

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Collen VonLv2
28 Sep 2019
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Related questions

Amino acid analysis of a decapeptide revealed the presenceof:

Asp Glu Tyr Arg Met Pro Lys Ser Phe

The following facts were observed:

Carboxypeptidase A or B treatment of the decapeptide had anyeffect

Trypsin treatment yielded two tetrapeptides and free Lys

Clostripain treatment yielded a tetrapeptide and ahexapeptide.

Cyanogen bromide treatment yielded an octapeptide and adipeptide of sequence Asn and Pro.

Chymotripsin treatment yielded two tripeptides and atetrapeptide. The N terminal chymotryptic peptide had a charge of-1 at neutral pH and a net charge of -3 at pH=12.

One cycle of Edman degradation gave PTH-Ser.

What is the amino acid sequence?

Amino acid analysis of a decapeptide revealed the presenceof:

Asp Glu Tyr Arg Met Pro Lys Ser Phe

The following facts were observed:

Carboxypeptidase A or B treatment of the decapeptide had anyeffect

Trypsin treatment yielded two tetrapeptides and free Lys

Clostripain treatment yielded a tetrapeptide and ahexapeptide.

Cyanogen bromide treatment yielded an octapeptide and adipeptide of sequence Asn and Pro.

Chymotripsin treatment yielded two tripeptides and atetrapeptide. The N terminal chymotryptic peptide had a charge of-1 at neutral pH and a net charge of -3 at pH=12.

One cycle of Edman degradation gave PTH-Ser.

What is the amino acid sequence?

2. Anoctapeptide was determined to have the following amino acidcomposition:

Lys (2), Phe (2), Gly (1), His (1),Leu (1), Met (1). The native peptide was run through one cycle ofthe Edman degradation and the PTH-leucine derivative was identifiedby HPLC. When the native peptide was exposed to cyanogen bromide(BrCN), a heptapeptide and free glycine were recovered. Incubationof the native protein with trypsin gave a tetrapeptide, atripeptide, and free lysine. The peptides were separated and eachrun through one cycle of the Edman degradation. The tetrapeptideyielded the PTH-leucine derivative, and the tripeptide yielded thePTH-phenylalanine derivative. Incubation of the native protein withpepsin produced a dipeptide and two tripeptides. The amino acidcomposition of the tripeptides (not the order) were determined tobe (Phe, Gly, Met) and (Phe, Lys, Lys). What is the sequence of theoctapeptide?

Show yourwork. 5 pts

Edman degredation—isolates N-terminal

Cyanogen Bromide—isolates C-terminal

Specificities of Proteases

BrCN cuts at the C-terminal side of Met

Trypsin cuts at the C-terminal side of Lys or Arg

Pepsin cuts at the N-terminal side of Phe, Trp or Tyr

An octapeptide contains the following amino acids: Gln, Glu, Gly, Thr, Arg, Tyr, Ile, Ser. Carboxypeptidase treatment of the octapeptide forms Thr and a heptapeptide. Treatment of the octapeptide with Trypsin forms forms two tetrapeptides, A and B. Treatment of A with Chymotrypsin yields two dipeptides, C and D. Edman degradation cleaves the following amino acids from each peptide: Gly (octapeptide), Gly (A), Ser (B), Gly (C), Ile(D). Partial hydrolysis of tetrapeptide B forms Ser-Glu in addition to other products. Deduce the structure of the octapeptide and fragments A-D.

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