Question

Keratin is the main structural protein in hair and cosists of two polypetides. Explain how the protein folds starting from the primary structure. Explain the different structures.

Answer 1

Answer-

1. Keratin is structural protein constitute major dry weight of hair, claws, nails, horns, hooves, quills etc. Structurally keratin is member of intermediate filament family .

2. Keratin is also known as alpha keratin as it is made from right handed alpha helix. Initially two strands of alpha helices are wrapped around each other parallely and this left handed supertwist formed which increases strength. The interaction between hydrophobic amino acids at the contact point of helices allows close packing of polypeptides as keratin is rich in hydrophobic amino acids Ala, Phe, Met, Val, Leu and Ile.

3. The individual alpha helix is secondary structure of keratin, coiled coil structure of alpha helices is tertiary structure of keratin and interwining if alpha helices is quaternary structure. The quaternary structure of keratin is stabilized by disulfide bonds.

4. When two coiled coil structure combines together this structure is known as protofilament that has diameter 20-30A°. Then two protofilament makes further structure known as protofibril. Then four protofibril combines to form one intermediate filament.