Correct option is A
Explanation-
Statement A: Collagen has a triple-helical domain structure which consists of three distinct α-chains.
Correct
Collagen is made of three polypeptide chains, commonly called α-chains. These three chains form a triple helix, a key feature of collagen’s structure.
Statement B: The collagen triple helix is stabilized by isoprenyl bonds.
Incorrect
Isoprenyl bonds are associated with lipid modifications (e.g., prenylation of proteins), not collagen. Correct stabilizing interactions in collagen: hydrogen bonding, especially involving hydroxyproline residues.
Statement C: Each α-chain has a left-handed polyproline II-type helix.
Correct
Each individual α-chain forms a left-handed helix resembling a polyproline II helix. The triple helix itself is right-handed, formed from three left-handed chains.
Statement D: Each α-chain is composed of multiple triplet sequences of Gly–Y–Z in which Y is commonly proline and Z is usually hydroxyproline.
Correct
The repeating unit of collagen is Gly–X–Y, where:
Glycine is always at every third residue (for tight packing), X is often proline, and Y is often hydroxyproline.
This repeat is essential for the triple-helical structure.
Since statement A, C and D are correct.
Therefore, the correct option is a - A, C, and D
