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A 310 helix is a type of secondary structure found (rarely) in proteins.
Structure
The amino acids in a 310-helix are arranged in a right-handed helical structure. Each amino acid corresponds to a 120° turn in the helix (i.e., the helix has three residues per turn), and a translation of 2.0 Å (= 0.2 nm) along the helical axis. Most importantly, the N-H group of an amino acid forms a hydrogen bond with the C = O group of the amino acid three residues earlier; this repeated i + 3 → i hydrogen bonding defines a 310-helix. Similar structures include the α-helix (i + 4 → i hydrogen bonding) and the π-helix i + 5 → i hydrogen bonding).
Residues in 310-helices typically adopt (φ, ψ) dihedral angles near (−49°, −26°). More generally, they adopt dihedral angles such that the ψ dihedral angle of one residue and the φ dihedral angle of the next residue sum to roughly −75°. For comparison, the sum of the dihedral angles for an α-helix is roughly −105°, whereas that for a π-helix is roughly −125°.
The general formula for the rotation angle Ω per residue of any polypeptide helix with trans isomers is given by the equation
See also
References
- Pauling L, Corey RB and Branson HR. (1951) "The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain", Proc. Nat. Acad. Sci. Wash., 37, 205.
| Protein secondary structure | ||
|---|---|---|
| Helices: | α-helix | 310 helix | π-helix | β-helix | Polyproline helix | Collagen helix | |
| Extended: | β-strand | Turn | Beta hairpin | Beta bulge | α-strand | |
| Supersecondary: | Coiled coil | Helix-turn-helix | EF hand | |
| Secondary structure propensities of amino acids | ||
| Helix-favoring: | Methionine | Alanine | Leucine | Glutamic acid | Glutamine | Lysine | |
| Extended-favoring: | Threonine | Isoleucine | Valine | Phenylalanine | Tyrosine | Tryptophan | |
| Disorder-favoring: | Glycine | Serine | Proline | Asparagine | Aspartic acid | |
| No preference: | Cysteine | Histidine | Arginine | |
| ←Primary structure | Tertiary structure→ | |
 |
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- This page was last modified on 30 January 2008, at 10:26.
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