Question

How do you name the polypeptide Ala-Ser-Gly-Val-Thr-Leu?

Answer 1

Polypeptides represent a class of chain of amino acids which are bonded by peptide bonds. A polypeptide contains both an N-terminus and a C-terminus residue like a single amino acid.

Complete step by step answer: A polypeptide is a long chain of amino acids held together by several peptide bonds. In general two to fifty amino acids are linked in a chain. They are named as dipeptide, tripeptide, tetrapeptide and so on.
The name of a peptide follows a certain pattern or rule. This is given as:
a. Identify the individual amino acid residues.
b. The name of the peptide begins with the name of the N-terminal amino acid residue.
c. The name of the intermediate residue lies in between.
d. The name of the peptide ends with the C-terminal amino acid residue.
The given polypeptide is Ala-Ser-Gly-Val-Thr-Leu. It consists of six different amino acids which are Alanine, Serine, Glycine, Valine, Threonine and Leucine. Except the C-terminal amino acid residues the rest of amino acids are named by substituting the ‘-ine’ of each amino acid with ‘-yl’.
Thus the name of the C-terminal amino acid remains as Leucine. The rest of the amino acid becomes Alanyl, Seryl, Glycyl, Valyl, and Threonyl.
Hence the name of the given polypeptide Ala-Ser-Gly-Val-Thr-Leu is Alanylglutamylglycylalanylleucine.

Note:
The functional attributes of the polypeptide depends on the N-terminal and the C-terminal amino acids. The positions of each amino acid in the chain is obtained with the help of peptide cleaving reagents. This leads to new N-terminal and C-terminal smaller peptide residues. A polypeptide with more than fifty amino acids constitutes a protein chain and several protein chains are linked together to form the RNA and DNA of our body.