October 23, 2016

Homework Help: Chemistry (Biochem)

Posted by Robert on Sunday, January 27, 2013 at 6:01pm.

I'm given two pictures looking down the alpha helices of a coiled coil dimer of alpha-keratin. I'm asked to identify three statements out of the following that are true. My guesses are 2, 3, and 6.

1. Leu-Glu-His-Val-Cys-Lys-Ser is a likely repeat in the α helix of keratin.

2. Each polypeptide in the dimer has 3.5 residues per turn, resulting in the slight winding, or twist, around the other polypeptide, that helps form the coiled coil.

3. The residues at positions b and c are less likely to be polar or charged because they are in contact with the solvent.

4. Keratin molecules are very strong due to hydrophilic interactions between charged amino acid side chains.

5. Lys-Val-Ser-Cys-Ser-Glu-Thr is a likely repeat in the α helix of keratin.

6. The α helix of the coiled coil is wound less tightly than predicted for an α helix.

7. α-Keratin is rich in Cys residues, enabling the formation of covalent cross-links between peptide chains and increasing the strength of the protein.

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