Question

What is the significance of the hydrophobic side chain each 3^rd or 4^th residue in an alpha-keratin?

Answer 1

Amino acids form a linear chain to give shape to the primary structure of a protein. This primary structure of a protein then folds into the secondary structure, -helix and -sheet. The folding of the primary structure into a secondary structure takes place due to non-covalent and hydrophobic interactions between the amino acid side chains and the amino acid side chain and the environment. -keratin is rich in alanine, leucine, arginine, and cysteine and has the structure right-handed -helix. In such alpha helices, every N−H group of the backbone donates an H-bond to the C=O group of the amino acid located 3 or 4 residues earlier along the protein sequence in the backbone. Hence, the hydrophobic side chains of each 3rd or 4th residue in an alpha keratin strand are responsible for the formation of an appropriate secondary alpha helix structure of the protein.

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