α-helix

Definition

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

5 Must Know Facts For Your Next Test

1. The α-helix structure was first proposed by Linus Pauling and Robert Corey in 1951.
2. Each turn of an α-helix consists of approximately 3.6 amino acid residues.
3. The hydrogen bonds that stabilize the α-helix form between the carbonyl oxygen of one amino acid and the amide hydrogen four residues away.
4. α-helices are often found in the regions of proteins that span cell membranes, such as transmembrane helices.
5. The side chains (R groups) of amino acids in an α-helix extend outward from the helical backbone, allowing for interactions with other molecules or protein domains.

Review Questions

• What type of bond stabilizes the α-helix structure?
• How many amino acid residues are typically found in one turn of an α-helix?
• In what type of protein regions are α-helices commonly found?

Related terms

β-sheet: A secondary structure in proteins 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 another.

Amino Acid:

The building blocks of proteins, consisting of a central carbon atom, an amino group, a carboxyl group, and a unique R side chain.