(3) Total hydrolysis of a small protein gives (3 Gly + lle + Leu + Lys +Phe+ Ser
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Question
(3) Total hydrolysis of a small protein gives (3 Gly + lle + Leu + Lys +Phe+ Ser+ Tyr +2 Val). Treat- ment with the Edman reagent liberates Ser. Treatment with carboxypeptidase liberates lle. Digestion with trypsin gives two fragments T1 and T2. Total hydrolysis of T1 gives (2 Gly + Lys+ Phe+Ser + 2 Val). Di- stion with chymotrypsin gives three fragments CH1, CH2, and CH3. Total hydrolysis of CH1 gives (lle + Leu; total hydrolysis of CH3 gives (3 Gly + Lys + Tyr). Deduce the primary structure of the protein.Explanation / Answer
Ans= Treatment with Edmann reagent liberated Ser. So Ser is on N terminus.
treatment with carboxypeptidase liberated Ile. So Ile is on C terminus.
Trypsin cleaves on carboxy side of Lysine and it has given 2 fragments.
Chymotrypsin acts on carboxy side of phe, tyr and it has given 3 fragments.
As ile is on C terminus of peptide, CH1 fragment on hydrolysis gives ile + leu so it is clear leu present before ile.
By analysing hydrolysed fragments and as per above information primary structure of protein is as follows.
Ser val val phe gly gly lys gly tyr leu ile
This sequence satisfies all the conditions provided in the question.
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