Please Help! And explain. Determine the amino acid sequence of an octapeptide wi
ID: 791652 • Letter: P
Question
Please Help! And explain.
Determine the amino acid sequence of an octapeptide with a composition of: 2 ile, 2 phe, 1 asp, 1 lys, 1 ala, 1 met When the octapeptide was subjected to partial acid hydrolysis, one of the products in the hydrolysate was the dipeptide: ile-ala chymotrypsin treatment of the intact octapeptide renders 2 tetrapeptides, each containing ile CNBr treatment of one of the tetrapeptides produces 2 dipeptides trypsin treatment of the same tetrapeptide gives a tripeptide and free phe One round of Edman degradation on the intact octapeptide released the following:Explanation / Answer
b) chymotrypsin cleves after Trp , Tyr , Phe hence it must clved octapeptide after Phe
it means Phe is at 4 th position as two tetrapeptides were obtained and also other Phe at last postion
c) CNBr clevage happens after Met residue hence one of tetratpeptide has Met ast 2nd position as two dipeptides were obtained hence Met must be either in 2nd from first or 2nd from last in octatpeptide sequence
d) Trypsin cleves after Lys or Arg , here clevage of tetrapeptide gave a tripeptide and Phe and hence
tetra peptide must have Lys at 3rd position , also it will have Met at second position ( from above)
e) Edman degradation identifies N terminal and its clear removing Ph-N=C=S group we get amino acid which is H2N-CH2(CH2COOH) - COOH which is aspratet Asp , hence Asp at 1st position
clubbing all these
a) one of peptide sequence given was Ile-Ala after partial hydrolysis , hence
we get Asp-ILe- Ala-Phe- ILe-Met-Lys-Phe