Chain-length dependence of alpha-helix to beta-sheet transition in polylysine: model of protein aggregation studied by temperature-tuned FTIR spectroscopy.
The chain-length dependence of the alpha-helix to beta-sheet transition in poly(L-lysine) is studied by temperature-tuned FTIR spectroscopy. This study shows that heterogeneous samples of poly(L-lysine), comprising polypeptide chains with various lengths, undergo the alpha-beta transition at an intermediate temperature compared to homogeneous ingredients. This holds true as long as each individual fraction of the polypeptide is capable of adopting an antiparallel beta-sheet structure. The tendency is that the longer chain is, the lower the alpha-beta transition temperature is, which has been linked to the presence of distorted or solvated helices with turns or beta sheets in elongating chains of poly(L-lysine). As such helical structures are apparently conducive to the alpha-beta transition, this draws a comparison to the hypothesis of metastable protein conformational states being a common stage in amyloid-formation pathways. The antiparallel architecture of the beta sheet is likely to reflect the pretransition interhelical interactions in poly(L-lysine). Namely, the chains are arranged in an antiparallel manner because of energetically favored antiparallel pre-assembly of dipolar alpha helices.
High Pressure Research Center, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland.
Wojciech
W
Dzwolak
Takeshi
T
Muraki
Minoru
M
Kato
Yoshihiro
Y
Taniguchi
D008970:Molecular Weight; D011107:Polylysine / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
D011107:Polylysine