Concept #1: Alpha Helix Hydrogen Bonding

Example #1: Which residue does the carbonyl group of the 21st residue of a 30 residue α-helix hydrogen bond to?

Practice: The oxygen-storage protein myoglobin has 8 α-helices in its single polypeptide chain. Its 67th residue is near the center of a 19 residue α-helix. Which residue does the amino group of myoglobin’s 67th residue hydrogen bond to?

Concept #2: Alpha Helix Dipole

Practice: True or False: Negatively charged residues near the α-helix N-terminal are stabilizing due to its net dipole.

Practice: Triose phosphate isomerase (TPI) is a crucial enzyme involved in the glycolysis pathway and contains 14 α-helices. Considering the net dipole of the α-helix, which of the following would be most destabilizing to TPI’s structure?

Practice: The hemagglutinin protein in influenza virus contains a remarkably long α-helix with 53 residues.

A. How long is the α-helix? _____________

B. How many turns does this α-helix have? _____________

C. How many hydrogen bonds are present in this α-helix? ______________

Practice: Which of the following statements about α-helices is false?