Complete hydrolysis of a heptapeptide showed that it has the following constituent amino acids:
2A, E, L, K, F, V
Deduce the amino acid sequence of this heptapeptide from the following data.
1. Treatment of the heptapeptide with 2, 4-dinitrofluorobenzene followed by incomplete hydrolysis gave, among other products: valine labeled at the a-amino group, lysine labeled at the e-amino group, and a dipeptide, DNP -- VL (DNP = 2, 4-dinitrophenyl-).
2. Hydrolysis of the heptapeptide with carboxypeptidase gave an initial high concentration of alanine, followed by a rising concentration of glutamic acid.
3. Partial enzymatic hydrolysis of the heptapeptide gave a dipeptide (A) and a tripeptide (B).
(a) Treatment of A with 2, 4-dinitrofluorobenzene followed by hydrolysis gave DNP-labeled leucine and lysine labeled only at the e-amino group.