The alpha helix Flashcards
What atoms are contained in a loop closed by each hydrogen bond within an alpha helix?
The loop contains 13 atoms - the carbonyl oxygen, 11 backbone atoms, and the amide hydrogen.
Example: The loop within an alpha helix contains 13 atoms.
What angles do the 4 and v angles of each residue in an alpha helix cluster around?
The 4 and v angles cluster around a @ value of -57° and a & value of -47°.
Example: The angles of each residue in an alpha helix cluster around specific values.
What is the average content of an alpha helix in proteins that have been examined?
The average content of an alpha helix in proteins that have been examined is 26%.
Example: The average content of an alpha helix in examined proteins is 26%.
Where are hydrophilic and hydrophobic amino acids typically located on an alpha helix?
Hydrophilic amino acids are on one face of the helix cylinder, while hydrophobic amino acids are on the opposite face.
Example: Hydrophilic and hydrophobic amino acids are typically located on opposite faces of an alpha helix.
What do amphipathic helices tend to do?
Amphipathic helices are often located on the surface of a protein with the hydrophilic side chains facing outward (toward the aqueous solvent) and the hydrophobic side chains facing inward (toward the hydrophobic interior).
Where do charged residues (asparagine, glutamate, aspartate, and arginine) tend to cluster?
Charged residues tend to cluster on one side of the helical wheel.
What example is given for an amphipathic helix on the surface of a protein?
The helix shown in Figures 4.11 and 4.12 is on the surface of the water-soluble liver enzyme alcohol dehydrogenase with the side chains of the first, fifth, and eighth residues.
What is shown in Figure 4.11?
View of a right-handed α helix. The blue ribbon indicates the shape of the polypeptide backbone. All the side chains, shown as ball-and-stick models, project outward from the helix axis. This example is from residues Ile-355 (bottom) to Gly-365 (top) of horse liver alcohol dehydrogenase. Some hydrogen atoms are not shown. [PDB 1ADF].
A right-handed α helix. This helix was created by Julian Voss-Andrea. It stands outside Linus Pauling’s childhood home in Portland, Oregon, United States.
