Helix geometry in proteins
DJ Barlow, JM Thornton - Journal of molecular biology, 1988 - Elsevier
DJ Barlow, JM Thornton
Journal of molecular biology, 1988•ElsevierIn this report we describe a general survey of all helices found in 57 of the known protein
crystal structures, together with a detailed analysis of 48 α-helices found in 16 of the
structures that are determined to high resolution. The survey of all helices reveals a total of
291 α-helices, 71 3 10-helices and no examples of π-helices. The conformations of the
observed helices are significantly different from the “ideal” linear structures. The mean φ, ψ
angles for the α-and 3 10-helices found in proteins are, respectively,(− 62°,− 41°) and …
crystal structures, together with a detailed analysis of 48 α-helices found in 16 of the
structures that are determined to high resolution. The survey of all helices reveals a total of
291 α-helices, 71 3 10-helices and no examples of π-helices. The conformations of the
observed helices are significantly different from the “ideal” linear structures. The mean φ, ψ
angles for the α-and 3 10-helices found in proteins are, respectively,(− 62°,− 41°) and …
Abstract
In this report we describe a general survey of all helices found in 57 of the known protein crystal structures, together with a detailed analysis of 48 α-helices found in 16 of the structures that are determined to high resolution.
The survey of all helices reveals a total of 291 α-helices, 71 310-helices and no examples of π-helices. The conformations of the observed helices are significantly different from the “ideal” linear structures. The mean φ, ψ angles for the α- and 310-helices found in proteins are, respectively, (−62 °, −41 °) and (−71 °, −18 °).
A computer program, HBEND, is used to characterize and to quantify the different types of helix distortion. α-Helices are classified as regular or irregular, linear, curved or kinked. Of the 48 α-helices analysed, only 15% are considered to be linear; 17% are kinked, and 58% are curved.
The curvature of helices is caused by differences in the peptide hydrogen bonding on opposite faces of the helix, reflecting carbonyl-solvent/side-chain interactions for the exposed residues, and packing constraints for residues involved in the hydrophobic core. Kinked helices arise either as a result of included proline residues, or because of conflicting requirements for the optimal packing of the helix side-chains.
In α-helices where there are kinks caused by proline residues, we show that the angle of kink is relatively constant (~26 °), and that there is minimal disruption of the helix hydrogen bonding. The proline residues responsible for the kinks are highly conserved, suggesting that these distortions may be structurally/functionally important.
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