α-helix

Definition

An α-helix is a common structural motif in proteins, characterized by a right-handed coiled or spiral conformation. It is stabilized by hydrogen bonds between the backbone atoms of the amino acids.

5 Must Know Facts For Your Next Test

1. The α-helix structure was first proposed by Linus Pauling in 1951.
2. It typically consists of 3.6 amino acids per turn of the helix.
3. The hydrogen bonds occur between the carbonyl oxygen of one amino acid and the amide hydrogen of another four residues earlier.
4. α-helices are often found in the hydrophobic core of globular proteins.
5. They can be disrupted by proline residues, which introduce kinks in the helical structure.

Review Questions

• What type of bond stabilizes an α-helix?
• How many amino acids are there per turn in an α-helix?
• Why do proline residues disrupt α-helices?

Related terms

β-sheet: A secondary protein structure characterized by beta strands connected laterally by at least two or three backbone hydrogen bonds.

Hydrogen Bond:

A weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other.

Secondary Structure:

The local folded structures that form within a polypeptide due to interactions between atoms of the backbone.