Question

The folds in collagen are due to?

• A. Glycine
• B. Alanine
• C. Arginine
• D. Histidine

Hint:

Which amino acid is small enough to sit at the crowded core of a triple helix?

Answer 1

The Correct Option is A

Step 1: Picture three left-handed alpha-chains coiling into a right-handed superhelix. The chains must approach very closely at the helix axis.

Step 2: Only an amino acid with a tiny side chain can occupy that axial position. Glycine, whose R group is a single hydrogen, fits perfectly, so it recurs as every third residue in the (Gly-X-Y)n motif.

Step 3: Larger residues such as alanine, arginine, or histidine would sterically clash and prevent tight winding. Thus the folding of collagen depends on glycine.

\[\boxed{\text{Glycine}}\]