Keratin is a coiledcoil protein Answer the following questio

Keratin is a \"coiled-coil\" protein. Answer the following questions about keratin. Keratin proteins have a \"pseudorepeat\" of how many residues? At what positions are hydrophobic residues found in the pseudorepeat? Why are there hydrophobic residues at those positions? Polar residues are usually found at the remaining positions. Why? Which of the following possible peptides is most likely to be a pseudorepeat? (pick only one) D-Q-1-E-V-E-R. W-Q-E-Y-E-R-D I-Q-E-V-E-R-D What is wrong, or less good, about the other two possibilities?

Solution

a. Keratin has pseudo repeats of 7 amino acids in its primary structure. The pseudo repeat is HxxHxxx. where the H is hydrophobic amino acid and X can be any amino acid.

b. The pseudo repeats contains hydrophobic amino acid at position one and three of the pseudo repeat.

c. They are present in those positions so that they can make up the hydrophobic side of the alpha helix of the keratin protein.

d. The other amino acids are not involved in formation of hydrophobic core of the keratin structure.

e. The option c sequence has possible peptide for pseudo repeat. Because it has hydrophobic amino acid iso leucine and valine at position one and three.

f. The sequence in option b is not good for pseudo repeat because it does not contain even a single hydrobhobic amino acid.