Question

24

Essentially all of the peptide bonds have trans-configuration to reduce steric clashes between groups attached to alpha – carbons of the neighboring amino-acids. Only one of the listed peptide bonds will have a high steric clash irrespective of whether it obtains cis- or trans- arrangement. The amino acid incorporated in such bond can sometimes “break” a peptide chain due to its unique structure. Select the peptide bond with that amino acid.

	a.	Lys-Ala
	b.	Lys-Ile
	c.	Lys-Asp
	d.	Lys-Pro

Answer 1

ANSWER - CORRECT OPTION IS D

out of all the amino acids, it is proline which have different structure because the R group present in proline not only binds to the central alpha carbon atom but also to a part of amino group as well . this causes the steric clashes. also out of the above all given amino acid it is proline which can exist in both cis and trans configuration and one should keep in mind that the polypeptide chain generally occur in trans configuration. therefore, correct option is D