A new perspective on beta-sheet structures using vibrational Raman optical activity: from poly(L-lysine) to the prion protein.
The vibrational Raman optical activity (ROA) spectrum of a polypeptide in a model beta-sheet conformation, that of poly(l-lysine), was measured for the first time, and the alpha-helix --> beta-sheet transition monitored as a function of temperature in H(2)O and D(2)O. Although no significant population of a disordered backbone state was detected at intermediate temperatures, some side chain bands not present in either the alpha-helix or beta-sheet state were observed. The observation of ROA bands in the extended amide III region assigned to beta-turns suggests that, under our experimental conditions, beta-sheet poly(L-lysine) contains up-and-down antiparallel beta-sheets based on the hairpin motif. The ROA spectrum of beta-sheet poly(L-lysine) was compared with ROA data on a number of native proteins containing different types of beta-sheet. Amide I and amide II ROA band patterns observed in beta-sheet poly(L-lysine) are different from those observed in typical beta-sheet proteins and may be characteristic of an extended flat multistranded beta-sheet, which is unlike the more irregular and twisted beta-sheet found in most proteins. However, a reduced isoform of the truncated ovine prion protein PrP(94-233) that is rich in beta-sheet shows amide I and amide II ROA bands similar to those of beta-sheet poly(L-lysine), which suggests that the C-terminal domain of the prion protein is able to support unusually flat beta-sheets. A principal component analysis (PCA) that identifies protein structural types from ROA band patterns provides a useful representation of the structural relationships among the polypeptide and protein states considered in the study.
McColl
Iain H
IH
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
Blanch
Ewan W
EW
Gill
Andrew C
AC
Rhie
Alexandre G O
AG
Ritchie
Mark A
MA
Hecht
Lutz
L
Nielsen
Kurt
K
Barron
Laurence D
LD
D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D036022:Capsid Proteins / Q000737:chemistry; D003208:Concanavalin A / Q000737:chemistry; D017909:Levivirus; D011107:Polylysine / Q000737:chemistry*; D011328:Prions / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012756:Sheep; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013381:Subtilisins / Q000737:chemistry; D010566:Virulence Factors, Bordetella / Q000737:chemistry
D001425:Bacterial Outer Membrane Proteins; D036022:Capsid Proteins; D011328:Prions; D010566:Virulence Factors, Bordetella; D003208:Concanavalin A; D011107:Polylysine; C068929:pertactin; D013381:Subtilisins