title: Requirement of Ala residues at g position in heptad sequence of alpha-helix-forming peptide for formation of fibrous structure.
abstract: 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.
authors.affiliation: Department of Physics; and Institute for Biomolecular Science, Faculty of Science, Gakushuin University, Mejiro, Tokyo 171-8588, Japan.
authors.forename: Gaku
authors.initials: G
authors.lastname: Aoki
authors.forename: Toyo K
authors.initials: TK
authors.lastname: Yamada
authors.forename: Mayu
authors.initials: M
authors.lastname: Arii
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kojima
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
mesh_terms: 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
chemical_list: D009842:Oligopeptides; D010455:Peptides; D000409:Alanine