You are investigating an alphahelix in your favorite protein

You are investigating an alpha-helix in your favorite protein. You note that the primary sequence is Ala-Val-Leu-Ile-His-Asp-Gln. Which amino acid N-H forms a hydrogen bond with the alanine carbonyl group?

A. Leu

B. Ile

C. His

D. Gln

Please explain how you got your answer. Is it as simple as I think? Do I just line them up?

Solution

C. His

In alpha-helix structure of protein there are 3.6 amino acid residues per turn of the helix. Hydrogen bonds are formed between backbone amino and carbonyl groups and those in the next turn of the helix.