The dimensions of an $\alpha$ helix from a fibrous protein such as keratin differ slightly from an $\alpha$ helix from a globular protein. What is the reason for this difference in helical dimensions?
A) An $\alpha$ helix from a fibrous protein is left-handed, not right-handed.
B) An $\alpha$ helix from a fibrous protein contains mainly hydrophobic residues, elongating the helix.
C) An $\alpha$ helix from a fibrous protein contains mainly polar residues, elongating the helix.
D) An$\alpha$ helix from a fibrous protein forms a coiled-coil, distorting the helix.
E) An $\alpha$ helix from a fibrous protein contains mainly Gly residues for more efficient packing.

Question

Quizplus · Accepted Answer

Fibrous proteins such as keratin often contain coiled-coil structures, which result from the winding together of two or more alpha helices. This coiled-coil structure distorts the individual helices, resulting in slightly different dimensions from helices found in globular proteins.

The Dimensions of An α\alphaα Helix from a Fibrous Protein Such as Keratin Differ Slightly

The Dimensions of An $\alpha$ Helix from a Fibrous Protein Such as Keratin Differ Slightly