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Chapter 28: Problem 40

After undergoing complete hydrolysis, a polypeptide yields the following amino acids: Ala, Gly, Lys, Ser, Phe. Partial hydrolysis yields the following fragments: Ala-Lys-Ser, Gly-Phe-Gly, Ser-Gly, Gly-Phe, Lys-Ser-Gly. An experiment using a marker establishes that Ala is the N-terminal amino acid. (a) Establish the amino acid sequence in this polypeptide. (b) What is the name of the polypeptide?

Short Answer

Expert verified
The amino acid sequence of the polypeptide is Ala-Lys-Ser-Gly-Phe-Gly.

Step by step solution

01

Determine the N-terminal

The experiment using a marker establishes that Ala is the N-terminal amino acid. Therefore, the sequence will start with Ala.
02

Identify the subsequent sequence

The partial hydrolysis suggests that Ala is followed by Lys and then Ser, giving us the following sequence: Ala-Lys-Ser. Note that the Lys-Ser-Gly fragment can be appended at the end based on only one fragment Ala-Lys-Ser containing Lys-Ser pair, and Ser is also succeeded by Gly in one of the fragments. Our sequence becomes Ala-Lys-Ser-Gly.
03

Complete the sequence

The remaining fragments Gly-Phe-Gly and Gly-Phe suggest that the next two amino acids will be Phe-Gly as Gly-Phe pair repeats twice. Therefore, the final amino acid sequence becomes: Ala-Lys-Ser-Gly-Phe-Gly.
04

Naming the Polypeptide

Polypeptides are usually referred to by their amino acid composition in the sequence, and are not typically given a distinct name. In this case, the polypeptide would be referred to by its amino acid composition sequence: Ala-Lys-Ser-Gly-Phe-Gly.

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Most popular questions from this chapter

Oleic acid is a moderately unsaturated fatty acid. Linoleic acid is polyunsaturated. What structural feature characterizes polyunsaturated fatty acids? Is stearic acid polyunsaturated? Is eleostearic acid? Why do you suppose safflower oil is so highly recommended in dietary programs?

Refer to a typical Escherichia coli bacterium. This is a cylindrical cell about \(2 \mu\) m long and \(1 \mu\)m in diameter, weighing about \(2 \times 10^{-12}\)g and containing about \(80 \%\) water by volume. The intracellular \(\mathrm{pH}\) is 6.4 and \(\left[\mathrm{K}^{+}\right]=1.5 \times 10^{-4} \mathrm{M}\) Determine the number of (a) \(\mathrm{H}_{3} \mathrm{O}^{+}\) ions and (b) \(\mathrm{K}^{+}\) ions in a typical cell.

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