Questions 1 and 2 (10 pts total): We discussed three methods for peptide digesti

Question

Questions 1 and 2 (10 pts total): We discussed three methods for peptide digestion analysis: i) cyanogen bromide (CNBr); ii) trypsin; and ii) chymotrypsin digestion. Two sets of digestion results are shown below. For each set... - indicate which reagent was used (based on the cleavage patterns) (2 pts); - reconstruct the original peptide sequence (2 pts); -predict the cuts from the digestion method aat used (1 pt) 1) Set 1... Set 1 Set 2 TFRAPRAP CYPLM LKMCY SFLKM HSMTE GYHSM PLMGY 2) Set 2... Set 1 LGMLF AIMLY VPMIC 2 Set GYAIM but was not analyzed. Edman degradation showed that the first two amino acids LEVPM are G and Y. The full-length peptide was known to consist of LZ amino acids. Comments: A dipeptide (two amino acid) fragment was isolated from each set

Explanation / Answer

1-

Set 1 - Cyanogen bromide cleaves at the C-terminal of Methionine residue. So set 1 is cleaved by cyanogen bromide.

set 2 - Chymotrypsin cleaves at the C-terminal of aromatic amino acids. So set 2 is cleaved by chymotrypsin.

From both the set we can make out the actual sequence of amino acid in the peptide.  

SFLKMCYPLMGYHSMTFRAP

Upon digestion, with trypsin, we will get

SFLK

MCYPLMGYHSMTFR

AP

2-

Set 2 - Cyanogen bromide cleaves at the C-terminal of Methionine residue. So set 2 is cleaved by cyanogen bromide.

Set 1 - Chymotrypsin cleaves at the C-terminal of aromatic amino acids. So set 1 is cleaved by chymotrypsin.

From both the set we can make out the actual sequence of amino acid in the peptide.  

GYAIMLYLGMLFVPMIC

This peptide cannot be cleaved by trypsin, as there are no lysine or arginine residues

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