135, Problem 2 - The following data was gathered in attempt...

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Problem 2 (Due September 27) The following information pertains to the sequencing problem below: Cysteine residues react with 2-bromoethylamine to generate derivatives in which the side-chain resembles that of lysine. Such modified side-chains are “recognized” by Trypsin, hence this protease cleaves on the C side of modified Cys (as well as K and R). Pepsin cleaves on the N side of L, F, W and Y as long as the other amino acid adjacent to the scissile bond is not Pro. The same constraint applies to the other enzymes used in the sequencing problem (Trypsin, Chymotrypsin and Carboxypeptidase A)-no cleavage occurs if one of the amino acids adjacent to the scissile peptide bond is Pro. B and Z are one letter symbols representing Asx and Glx, and are used when there is no information as to whether aspartic acid/asparagine (B) or glutamic acid/glutamine (Z) is present. Iodoacetate alkylates cysteine SH groups so as to prevent their oxidation to disulfides.
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Unformatted text preview: The following data was gathered in attempt to sequence an oligopeptide: 1) Complete acid hydrolysis: (B, 2C, F, G, I, K, L, M, P, R, S) 2) One cycle of Edman degradation: L, S 3) Carboxypeptidase A treatment (sufficient time to remove one a.a. per chain): D 4) Treatment with DTT and iodoacetate followed by Trypsin hydrolysis (the letters inside the parentheses represent the a.a. composition of the fragments; modified cys are represented by C): (R, S), (D,M), (C, F, G, I, L, P), (C, K) 5) Treatment with DTT and 2-bromoethylamine followed by Trypsin hydrolysis: (R, S), (D, M), (C ), (C, G, L), (F, I, P), (K) 6) Treatment with Chymotrypsin: No fragments 7) Treatment with Pepsin: (2C, D, G, K, L, M, R, S), (F, I, P) Provide the primary structure of the oligopeptide, showing the reasoning that led to your final result....
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This note was uploaded on 03/03/2011 for the course CHEM 135 at San Jose State University .

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