A d-amino acid would interrupt an $\alpha$ helix made of l-amino acids.Another naturally occurring hindrance to the formation of an$\alpha$ helix is the presence of:
A)a negatively charged Arg residue.
B)a nonpolar residue near the carboxyl terminus.
C)a positively charged Lys residue.
D)a Pro residue.
E)two Ala residues side by side.

Question

Quizplus · Accepted Answer

Proline is known to interrupt the formation of alpha helices due to its rigid cyclic structure and inability to form a hydrogen bond with the amide nitrogen of the amino acid in the following turn of the helix. Therefore, the presence of a Pro residue would hinder the formation of the F1F1F1S1F1F1F10 helix.

A D-Amino Acid Would Interrupt An α\alphaα Helix Made of L-Amino Acids

A D-Amino Acid Would Interrupt An $\alpha$ Helix Made of L-Amino Acids