View source for Peptide plane flipping

'''Peptide plane flipping''' is a type of [[conformational change]] that can occur in [[protein]]s by which the [[dihedral angle]]s of adjacent [[amino acid]]s undergo large-scale rotations with little displacement of the [[side chain]]s. The plane flip is defined as a rotation of the dihedral angles φ,ψ at amino acids ''i'' and ''i+1'' such that the resulting angles remain in structurally stable regions of [[Ramachandran space]].  The key requirement is that the ''sum'' of the ψ<sub>''i''</sub> angle of residue ''i'' and the φ<sub>''i+1''</sub> angle of residue ''i+1'' remain roughly constant; in effect, the flip is a [[crankshaft]] move about the axis defined by the C<sup>α</sup>-Cˡ and N-C<sup>α</sup> bond vectors of the peptide group, which are roughly parallel.  As an example, the type I and type II [[turn (biochemistry)|beta turns]] differ by a simple flip of the central [[peptide bond|peptide group]] of the turn.  

Peptide plane flips have been observed in the dynamics of [[native state]] protein [[tertiary structure]]s by comparing crystal structures of the same proteins in multiple conformations. However, the most important role of plane flipping is thought to be in the process of early [[protein folding]] rather than native-state local fluctuations.<ref name="Hayward">Hayward S. (2001). Peptide-plane flipping in proteins. ''Protein Sci'' 10(11):2219-27. PMID 11604529</ref> 

Peptide plane flipping provides a relatively low-energy pathway from [[alpha sheet]] or left-handed [[alpha helix]] to [[beta strand]] conformations. This has been suggested as a mechanism in the conformational changes of [[amyloid beta]] and related [[amyloid]]ogenic [[peptide]]s implicated in protein misfolding diseases such as [[Alzheimer's disease]]. These peptides may pass through an alpha-sheet intermediate in forming the beta-sheet-rich amyloid fiber assembly.<ref name="Daggett">Daggett V. (2006). Alpha-sheet: The toxic conformer in amyloid diseases? ''Acc Chem Res'' 39(9):594-602. PMID 16981675</ref><ref name="Armen">Armen RS, DeMarco ML, Alonso DO, Daggett V. (2004). Pauling and Corey's alpha-pleated sheet structure may define the prefibrillar amyloidogenic intermediate in amyloid disease. ''Proc Natl Acad Sci USA'' 101(32):11622-7. PMID 15280548</ref>

==References==
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[[Category:Protein structure]]
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