310 helix

The 310 -helix (3.0 residues per 360 ° rotation, 10-membered ring of the hydrogen bonds ) is a secondary structure motif of peptides and proteins, which can be connected to the ends of the α -helices and appear separately, and about 10 % of the accounts helix proportion of globular proteins. She is a right-handed helix with about three amino acid side chains per revolution. The 310- helix is stabilized by intramolecular C = O • • • HN hydrogen bonds between the nth and the (n 3 ) th amino acid. Due to this hydrogen bond, a ring with ten bonds is formed, which corresponds to the structure of a β - loop of subtype III. The van der Waals contacts and hydrogen bonds are not as optimal as that of the α -helix in proteins, so that often only a short 310- helices occur two to three hydrogen bonds.