'''Peptide plane flipping''' is a type of conformational change that can occur in proteins by which the dihedral angles of adjacent amino acids undergo large-scale rotations with little displacement of the side chains. 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>-C¹ 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 beta turns differ by a simple flip of the central peptide group of the turn.
==In protein dynamics== The significance of peptide plane flips in the dynamics of the native state has been inferred in some proteins by comparing crystal structures of the same protein in multiple conformations.<ref name="Hayward">{{Cite journal | doi = 10.1110/ps.23101 | last1 = Hayward | first1 = S. | year = 2001 | title = Peptide-plane flipping in proteins | journal = Protein Sci | volume = 10 | issue = 11| pages = 2219–27 | pmid = 11604529 | pmc = 2374056 }}</ref> For example, peptide flips have been described as significant in the catalytic cycle of flavodoxin<ref name="ludwig">{{cite journal|last1=Ludwig|first1=ML|last2=Pattridge|first2=KA|last3=Metzger|first3=AL|last4=Dixon|first4=MM|last5=Eren|first5=M|last6=Feng|first6=Y|last7=Swenson|first7=RP|title=Control of oxidation-reduction potentials in flavodoxin from Clostridium beijerinckii: the role of conformation changes.|journal=Biochemistry|date=11 February 1997|volume=36|issue=6|pages=1259–80|pmid=9063874|doi=10.1021/bi962180o}}</ref> and in the formation of amyloid structures, where their ability to provide a low-energy pathway between beta sheet and the so-called alpha sheet conformation is suggested to facilitate the early stages of amyloidogenesis.<ref name="milner-white">{{cite journal|last1=Milner-White|first1=JE|last2=Watson|first2=JD|last3=Qi|first3=G|last4=Hayward|first4=S|title=Amyloid formation may involve alpha- to beta sheet interconversion via peptide plane flipping.|journal=Structure|date=September 2006|volume=14|issue=9|pages=1369–76|pmid=16962968|doi=10.1016/j.str.2006.06.016|doi-access=free}}</ref><ref name="Daggett">{{Cite journal | doi = 10.1021/ar0500719 | last1 = Daggett | first1 = V. | author-link = Valerie Daggett | year = 2006 | title = Alpha-sheet: The toxic conformer in amyloid diseases? | journal = Acc Chem Res | volume = 39 | issue = 9| pages = 594–602 | pmid = 16981675 }}</ref><ref name="Armen">{{Cite journal | doi = 10.1073/pnas.0401781101 | last1 = Armen | first1 = RS | last2 = DeMarco | first2 = ML | last3 = Alonso | first3 = DO | last4 = Daggett | first4 = V. | year = 2004 | title = Pauling and Corey's α-pleated sheet structure may define the prefibrillar amyloidogenic intermediate in amyloid disease | journal = Proc Natl Acad Sci USA | volume = 101 | issue = 32| pages = 11622–7 | pmid = 15280548 | pmc = 511030 | bibcode = 2004PNAS..10111622A | doi-access = free }}</ref> Peptide plane flipping may also be significant in the early stages of protein folding.<ref name=Hayward />
==In crystallography== In protein structures determined by X-ray crystallography, poor peptide-plane geometry has been described as a common problem; many structures need correction by peptide-plane flips or peptide bond flips.<ref>{{cite journal |last1=Touw |first1=WG |last2=Joosten |first2=RP |last3=Vriend |first3=G |title=Detection of trans-cis flips and peptide-plane flips in protein structures. |journal=Acta Crystallographica Section D |date=August 2015 |volume=71 |issue=Pt 8 |pages=1604–14 |doi=10.1107/S1399004715008263 |pmid=26249342|pmc=4528797 |bibcode=2015AcCrD..71.1604T }}</ref>
==References== {{reflist|30em}}
Category:Protein structure
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