Questions 1) Determine the single letter code 40 amino acid sequence of the venom peptide by explaining the result of each experiment. 2) Draw the structure of the peptide EAVRLFI, and identify a) carbons alpha b) peptide bonds. 3) Calculate the isoelectric point of the peptide EAVRLFI. 4) Draw a schematic representation of paper electrophoresis at pH 7 of the molecules treated by Asp-N endopeptidase. Explain your result.
A peptide composed of 40 amino acids (aa) was isolated from the venom of the Gila Monster
(Heloderma suspectum, then submitted to various biochemical and chemical treatments.
1) After a treatment with a highly specific chymotrypsin, four peptides were generated:
- peptide A (6 aa)
- peptide B (16 aa)
- peptide C (3 aa)
- , and peptide D (15 aa)
2) Treatment with carboxypeptidases A or B resulted in the release of:
- phenylalanine for peptides A and B
- tryptophan for peptide C
- glycine for peptide D and the 40 amino acids venom peptide
3) One cycle of Edman degradation either for peptide A or for the 40 amino acids
peptide gave the exact PTH derivative indicated below:
4) The 40 amino acids peptide treated with Asp-N endopeptidase followed by mass
spectrometry MS/MS revealed the following composition:
- two molecules of glutamic acid,
- various peptides indicated below sorted by masses:
HG,
DLSKQM,
EGTFTS,
EAVRLFI,
EWLKNGGPSSGAPPPSG
Information
- Chymotrypsin (endopeptidase) hydrolyzes peptide bonds on the C-terminus of a
peptide bond of an
- Carboxypeptidase A (exopeptidase) hydrolyzes peptide bonds of a peptide at the C-
terminus of a protein or peptide, except for Pro, Lys, and Arg
- Carboxypeptidase B (exopeptidase) hydrolyzes peptide bonds of a peptide at the C-
terminus of a protein or peptide, on Arg or Lys
- Asp-N (endopeptidase) hydrolyzes peptide bonds on the N-terminal side of aspartic and
glutamic acid residues (D, E)
Questions
1) Determine the single letter code 40 amino acid sequence of the venom peptide by
explaining the result of each experiment.
2) Draw the structure of the peptide EAVRLFI, and identify
a) carbons alpha
b) peptide bonds.
3) Calculate the isoelectric point of the peptide EAVRLFI.
4) Draw a schematic representation of paper electrophoresis at pH 7 of the molecules treated
by Asp-N endopeptidase. Explain your result.
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