Chapter 10, Problem 4P

The lipid portion of a typical bilayers is about ${\text{30 A}}^{\text{0}}$ thick.

a. Calculate the minimum number of residues in an $\text{α}$ -helix required to span this distance.

b. Calculate the minimum number of residues in an $\text{β}$ -strand required to span this distance.

c. Explain why $\text{α}$ -helices are most commonly observed in transmembrane protein sequences when the distance from one side of a membrane to the other can be spanned by significantly fewer amino acids in $\text{β}$ -strand conformation.

d. The epidermal growth factor receptor has a single transmembrane helix. Find it in this partial sequence:

...RGPKIPSIATGMVGALLLLVVALGIGILFMRRRH…