You have been given the assignment in the laboratory to sequence a protein. You

Question

You have been given the assignment in the laboratory to sequence a protein. You know from the molecular weight and other indicators that this peptide is 20 amino acids long. Using your molecular tool box you begin to treat the protein with the following proteases: carboxypeptidase, chymotrypsin, trypsin, pepsin, Asp-N-Protease and aminopeptidase. Referring back to the textbook of biochemistry, you know that carboxypeptidase cleaves the terminal amino acid at the carboxyl end of the protein and that aminopeptidase cleaves the terminal amino acid at the amino terminal end of the protein. Trypsin cleaves the peptide at the carboxyl side of lysine and arginine residues. Chymotrypsin cleaves the peptide at the carboxyl side of phenylalanine, tryptophan, and tyrosine. Asp-N-Protease cleaves the peptide at the amino side of asparagine and glutamate. Results from your experiment are as follows:

[Below are examples of proteases of how its broken down]

(a) Treatment with carboxypeptidase gives you free leucine and a 19 amino acid long peptide

(b) Treatment with amino peptidase gives you free glutamate and a 19 amino acid long peptide.

(c) Treatment with pepsin gives you the following peptide segments:
PHE-SER-LYS-CYS-GLU-VAL
PHE
GLU-ALA
TYR-ILU-MET-ASP-LYS
TRP-ARG-MET-ASP-GLU-LEU

(d) Treatment with trypsin gives you the following peptide segments:
PHE-TRP-ARG
GLU-ALA-PHE-SER-LYS
MET-ASP-GLU-LEU
CYS-GLU-VAL-TYR-ILU-MET-ASP-LYS

(e) Treatment with Asp-N-Protease gives you the following peptide segments:
ASP
GLU-VAL-TYR-ILU-MET
GLU-ALA-PHE-SER-LYS-CYS
GLU-LEU
ASP-LYS-PHE-TRP-ARG-MET

(f) Treatment with chymotrypsin gives you the following peptide segments:
GLU-ALA-PHE
ILU-MET-ASP-LYS-PHE
SER-LYS-CYS-GLU-VAL-TYR
TRP
ARG-MET-ASP-GLU-LEU

Sequence the protein and draw in the format from amino to carboxyl (left to right) using the three letter format for each amino acid (as shown above in the peptide segments).

Explanation / Answer

(f) Treatment with chymotrypsin gives you the following peptide segments: GLU-ALA-PHE ILU-MET-ASP-LYS-PHE SER-LYS-CYS-GLU-VAL-TYR TRP ARG-MET-ASP-GLU-LEU

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.