Given the following information about a polypeptide
Hydrolysis of the polypeptide gives the following amino acids: Arg; Gly; Lys; Met(3) ; Phe(2);
Ser(2) ; Tyr.
Treatment of the polypeptide with chymotrypsin gives the following fragments: Met-Lys-Ser-Phe; Ser-Gly-Tyr; Met-Arg-Phe; Met.
Treatment of the polypeptide with cyanogen bromide gives the following fragments:
Ser-Gly-Tyr-[lactone]; Arg-Phe-[lactone]; Lys-Ser-Phe-[lactone].
Sanger degradation gives 2,4-DNP-Ser.
What is the primary structure of the original polypeptide?

Question

Given the following information about a polypeptide
Hydrolysis of the polypeptide gives the following amino acids: Arg; Gly; Lys;  Met(3) ; Phe(2);
 Ser(2) ;  Tyr.
Treatment of the polypeptide with chymotrypsin gives the following fragments: Met-Lys-Ser-Phe; Ser-Gly-Tyr; Met-Arg-Phe; Met.
Treatment of the polypeptide with cyanogen bromide gives the following fragments:
Ser-Gly-Tyr-[lactone]; Arg-Phe-[lactone]; Lys-Ser-Phe-[lactone].
Sanger degradation gives 2,4-DNP-Ser.
What is the primary structure of the original polypeptide?

Quizplus · Accepted Answer

The Sanger degradation indicates that Ser is the N-terminal amino acid. Chymotrypsin cleaves at the carboxyl side of Phe, Tyr, and Trp, and cyanogen bromide cleaves at the carboxyl side of Met. The fragments from both treatments align with the sequence in option A.

Given the Following Information About a Polypeptide