Before starting the problem consider the peptide Ala-Lys-Ala-Lys-Asp. Digestion by trypsin produces 3
fragments but only 2 unique fragments. The 2 unique fragments are Ala-Lys and Asp.
You have been assigned the task of determining the sequence of a 25-residue polypeptide from the
following data. If no subscript is given then the number is 1.
1. The AA composition is Ala3, Arg3, Asp, Cys, Glu6, Gly, His, Ile, Lys, Met2, Ser, Trp2, Tyr, Val
2. Edman degradation of intact polypeptide indicated the N-terminal sequence is Cys-His-Glu-Ser
3. Digestion by trypsin produced 5 unique fragments --