Assistance with number 5 please ) All residues in that peptide were adopting an

Question

Assistance with number 5 please ) All residues in that peptide were adopting an alpha-helical conformation l residues in that peptide were adopting a beta-strand conformation >Al Question 5. Keratin is a "coiled-coil" protein. Answer the following questions about keratin. (a) Keratin proteins have a "pseudorepeat" of how many residues? (b) At what positions are hydrophobic residues found in the pseudorepeat? (c) Why are there hydrophobic residues at those positions? (d) Polar residues are usually found at the remaining positions. Why? (e) Which of the following possible peptides is most likely to be a pseudorepeat? (pick only one) a. D-Q-I-E-V-E-R b. W-Q-E-Y-E-R-D c. I-Q-E-V-E-R-D (0) What is wrong, or less good about the other two possibiliti e each of the th Question 6 (a) Using the table of AA propensities from the book, rat peptides beloVior its likelihood to be found in either an -helix or a -sheet, by addi up the values for each amino acid in each conformation (b) Now, check each peptide for "sequence busters" - amino acids and groups of ami acids that are hardly ever found in helices or sheets (these are listed in the text) (c) Pick the one sequence most likely to be in a helix and the one most likely to be in sheet and justify your choice based on your work above in (a) and (b)

Explanation / Answer

Ans: Keratin has 7 residue pseudorepeat. Explained below.

Ans B: keratin contains a 7 residue pseudorepeat (a-b-c-d-e-f-g) within the central ~310 segment of the molecule.

Residue a and d are non-polar and are responsible for the association of the two subunits. Usually it is the leucine residue present D. The B and C residues are hydrophilic.

c. The 5.1 Å spacing of the alpha-helices optimize the association of the hydrophobic residues. The a and d residue line up along one side of the helix. This region always gets associated with the hydrophobic region of other helix and combine.

ans d: the cysteine residue is high in the keratin structure with disulfide bridges which is the polar groupamino acid.

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