Due to the high abundance of glycine and proline contents, collagen fails to form a regular α-helix and β-sheet structure. Three left-handed helical strands twist to form a right-handed triple helix. A collagen triple helix has 3.3 residues per turn.

Does collagen have three alpha helices?

The Basic Structural Unit of Collagen Is a Triple Helix

Its fundamental structural unit is a long (300-nm), thin (1.5-nm-diameter) protein that consists of three coiled subunits: two α1(I) chains and one α2(I).

Is collagen made of helices?

Collagen is the most abundant protein in animals. This fibrous, structural protein comprises a right-handed bundle of three parallel, left-handed polyproline II-type helices. Much progress has been made in elucidating the structure of collagen triple helices and the physicochemical basis for their stability.