Chapter 5, Problem 8P

Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book.

1. Solving the Sequence of an Oligopeptide From Sequence Analysis Data

Amino acid analysis of an oligopeptide containing nine residues revealed the presence of the following amino adds:

Arg Cys Gly Leu Met Pro Tyr Val

The following was found:

1. Carboxypeptidase A treatment yielded no free amino add.
2. Edman analysis of the intact oligopeptide released

c. Neither trypsin nor ehymotrypsin treatment of the nonapeptide released smaller fragments. However, combined trypsin and chymotrypsin treatment liberated free Arg.

1. CNBr treatment of the eight-residue fragment left after combined trypsin and chymotrypsin action yielded a six-residue fragment containing Cys* Gly. Pro, Tyr, and Val and a dipeptide.
2. Treatment of the six-residue fragment with β-mercaptoethanol yielded two tripeptidcs. Brief Edman analysis of the tripeplide mixture yielded only ΡÎ�Ή-Cys. (The sequence of each tripeptide, as read from the N-terminal end, is alphabetical if the one-lelter designation for amino acids is used.)

What is the amino acid sequence of this nonapeptide?