An Octapeptide Was Determined to Have the Following Amino Acid

Multiple Choice

An octapeptide was determined to have the following amino acid composition: Lys 2) , Phe 2) , Gly 1) , His 1) , Leu 1) , Met 1) . The native peptide was run through one cycle of the Edman degradation and the PTH-leucine derivative was identified by HPLC. When the native peptide was exposed to cyanogen bromide CNBr) , a heptapeptide and free glycine were recovered. Incubation of the native protein with trypsin gave a tetrapeptide, a tripeptide, and free lysine. The peptides were separated and each run through one cycle of the Edman degradation. The tetrapeptide yielded the PTH-leucine derivative, and the tripeptide yielded the PTH-phenylalanine derivative. Incubation of the native protein with pepsin produced a dipeptide and two tripeptides. The amino acid composition of the tripeptides not the order) were determined to be Phe, Gly, Met) and Phe, Lys, Lys) . What is the sequence of the octapeptide?
Specificities of Proteases
BrCN cuts at the C-terminal side of Met Trypsin cuts at the C-terminal side of Lys or Arg
Pepsin cuts at the N-terminal side of Phe, Trp or Tyr

A) Leu-His-Phe-Lys-Lys-Phe-Met-Gly
B) Gly-Met-Phe-Lys-Lys-Phe-His-Leu
C) Met-Leu-Phe-Lys-Phe-Gly-Lys-His
D) Leu-His-Lys-Lys-Phe-Phe-Gly-Met
E) His-Phe-Leu-Lys-Lys-Phe-Met-Gly