Question

A nonapeptide was treated with 6N HCl at 110 oC for 24 hours and was determined to have the following amino acid composition: (Lys)2, (Gly)2, Met, Leu, (Phe)2, His. The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then, hydrolyzed by a strong acid. 2,4-Dinitrophenylhistidine derivative was identified by the HPLC. When the native peptide was exposed to cyanogen bromide (CNBr), an octapeptide and a free glycine were recovered. Incubation of the native peptide with trypsin gave a pentapeptide, a tripeptide, and a free Lys. 2,4-Dinitrophenylhistidine was recovered from the pentapeptide, and 2,4-dinitrophenyl-phenylalanine was recovered from the tripeptide. What is the native sequence of this nonapeptide? Explain rational behind your answer.

Answer 1