Requirement of Ala residues at g position in heptad sequence of alpha-helix-forming peptide for formation of fibrous structure.
One feature of the alpha3-peptide, which has the amino acid sequence of (Leu-Glu-Thr-Leu-Ala-Lys-Ala)(3), that distinguishes it from many other alpha-helix-forming peptides is its ability to form fibrous assemblies that can be observed by transmission electron microscopy. In this study, the effects of Ala-->Gln substitution at the e (5th) or g (7th) position in the above heptad sequence of the alpha3-peptide on the formation of alpha-helix and fibrous assemblies were investigated by circular dichroism spectral measurement and atomic force microscopy. The 5Qalpha3-peptide obtained by Ala-->Gln substitution at the e position of the alpha3-peptide was found to form very short fibrils with long-elliptical shape, whereas the 7Qalpha3-peptide with Gln residues at the g position lost its ability to form such assemblies, in spite of alpha-helix formation in both peptides; the stabilities of both peptides decreased. These results indicate that Ala residues at the g position in the heptad sequence of the alpha3-peptide are key residues for the formation of fibrous assemblies, which may be due to hydrophobic interactions between alpha-helical bundle surfaces.
Aoki
Gaku
G
Department of Physics; and Institute for Biomolecular Science, Faculty of Science, Gakushuin University, Mejiro, Tokyo 171-8588, Japan.
Yamada
Toyo K
TK
Arii
Mayu
M
Kojima
Shuichi
S
Mizoguchi
Tadashi
T
D000409:Alanine / Q000737:chemistry* / Q000235:genetics; D019943:Amino Acid Substitution; D002942:Circular Dichroism; D018625:Microscopy, Atomic Force; D009842:Oligopeptides / Q000737:chemistry* / Q000235:genetics; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary
D009842:Oligopeptides; D010455:Peptides; D000409:Alanine