Abstract
The vibrational Raman optical activity (ROA) spectrum of a polypeptide in a model β-sheet conformation, that of poly(L-lysine), was measured for the first time, and the α-helix → β-sheet transition monitored as a function of temperature in H2O and D2O. Although no significant population of a disordered backbone state was detected at intermediate temperatures, some side chain bands not present in either the α-helix or β-sheet state were observed. The observation of ROA bands in the extended amide III region assigned to β-turns suggests that, under our experimental conditions, β-sheet poly(L-lysine) contains up-and-down antiparallel β-sheets based on the hairpin motif. The ROA spectrum of β-sheet poly(L-lysine) was compared with ROA data on a number of native proteins containing different types of β-sheet. Amide I and amide II ROA band patterns observed in β-sheet poly(L-lysine) are different from those observed in typical β-sheet proteins and may be characteristic of an extended flat multistranded β-sheet, which is unlike the more irregular and twisted β-sheet found in most proteins. However, a reduced isoform of the truncated ovine prion protein PrP94-233 that is rich in β-sheet shows amide I and amide II ROA bands similar to those of β-sheet poly(L-lysine), which suggests that the C-terminal domain of the prion protein is able to support unusually flat β-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.
Original language | English |
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Pages (from-to) | 10019-10026 |
Number of pages | 7 |
Journal | Journal of the American Chemical Society |
Volume | 125 |
Issue number | 33 |
DOIs | |
Publication status | Published - 20 Aug 2003 |