A nonapeptide was determined to have the following amino acid composition: (Lys)2, (Gly) 2,(Phe) 2, His, Leu, Met. The native peptide was incubated with 1-fluoro-2,4- dinitrobenzene(FDNB) and then hydrolyzed; 2,4-dinitrophenylhistidine was identified by HPLC. When thenative peptide was exposed to cyanogen bromide (CNBr), an octapeptide and free glycinewere recovered. Incubation of the native peptide with trypsin gave a pentapeptide, atripeptide, and free Lys. 2,4-Dinitrophenyl-histidine was recovered from the pentapeptide,and 2,4-dinitrophenylphenylalanine was recovered from the tripeptide. Digestion with theenzyme pepsin produced a dipeptide, a tripeptide, and a tetrapeptide. The tetrapeptide wascomposed of (Lys) 2, Phe, and Gly. The native sequence was determined to be:Met-Leu-Phe-Lys-Phe-Gly-Gly-Lys-HisHis-Leu-Gly-Lys-Lys-Phe-Phe-Gly-MetHis-Phe-Leu-Gly-Lys-Lys-Phe-Met-GlyGly-Phe-Lys-Lys-Gly-Leu-Met-Phe-His● His-Leu-Phe-Gly-Lys-Lys-Phe-Met-Gly

Trypsin - Cleaves at Carboxyl terminus of basic amino acid such as lysine and arginine. Ahead of amino acid towards C terminalPepsin - Cleaves at at C terminus of aromatic amino acid like phenylalanine, tyrosine, tryptophan and Leucine. Ahead of amino acid towards C terminal.Cyanogen Bromide (CNBr) - Cuts at methionine residue on the C - terminal of peptide.1-Fluro-2,4-dintrobenzene (FDNB) - It is Sanger's reagent used for end peptide detection and the labelling is performed in N-terminal of polypeptide.2,4-Ddintrophenylhistidine (2,4 DNP) - This compound useful in estimation or detection of carbonyl groups like aldehydes and ketones (either of the two) group in any chemical species. This is also known as Brady's reagent. The method involves segregation aldehyde and ketone functional group containing species from each other and also it is reversible process.Hydrolysis - This process generates free amino acids as it cleaves the covalent bond in the polypeptides such as peptide bond.We can find out native sequence from the given information about treatment with chemical compounds and enzymes.Given content of polypeptideLys(2), Gly(2), Phe(2), His, Leu, Met. Total = 9Procedure AStep 1. Native polypeptide + FDNB N terminal labelling AStep 2. A B + 2,4 Dinitrophenyl histadine (HPLC detect)Step 3. Native polypeptide + CNBr C(Octapeptide) + Met C-terminal (C is native polypeptide without C-terminus Met) Procedure BNative polypeptide +Trypsin Pentapeptide (5) + Tripeptide (3) + Lys (1) Total = 9.(2,4 Dinitrophenyl histadine recovered from pentapeptide) (2,4DNP from tripeptide) 2. Native Polypeptide + Pepsin Dipeptide (2) + Tripeptide (3) + Tetrapeptide (4)[Tetrapeptide (Lys (2), Phe, Gly)]Trypsin - 5,3,1Pepsin - 2,3,4 4. Gly-Phe-Lys-Lys-Gly-Leu-Met-Phe-HisTrypsin - 5,3,1Pepsin - 2,3,4Native sequence is 2nd is answer. C-His-Leu-Gly-Lys-Lys-Phe-Phe-Gly-Met-N.As CNBr cuts at C terminal Methonine.