title: Role of positions e and g in the fibrous assembly formation of an amphipathic α-helix-forming polypeptide.
abstract: We previously characterized α3, a polypeptide that has a three times repeated sequence of seven amino acids (abcdefg: LETLAKA) and forms fibrous assemblies composed of amphipathic α-helices. Upon comparison of the amino acid sequences of α3 with other α-helix forming polypeptides, we proposed that the fibrous assemblies were formed due to the alanine (Ala) residues at positions e and g. Here, we characterized seven α3 analog polypeptides with serine (Ser), glycine (Gly), or charged residues substituted for Ala at positions e and g. The α-helix forming abilities of the substituted polypeptides were less than that of α3. The polypeptides with amino acid substitutions at position g and the polypeptide KEα3, in which Ala was substituted with charged amino acids, formed few fibrous assemblies. In contrast, polypeptides with Ala replaced by Ser at position e formed β-sheets under several conditions. These results show that Ala residues at position e and particularly at position g are involved in the formation of fibrous assemblies.
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba, Japan; Institute for Biomolecular Science, Gakushuin University, Tokyo, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Takei
authors.forename: Kouhei
authors.initials: K
authors.lastname: Tsumoto
authors.forename: Masakuni
authors.initials: M
authors.lastname: Yoshino
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kojima
authors.forename: Kazumori
authors.initials: K
authors.lastname: Yazaki
authors.forename: Takuya
authors.initials: T
authors.lastname: Ueda
authors.forename: Tsunetomo
authors.initials: T
authors.lastname: Takei
authors.forename: Fumio
authors.initials: F
authors.lastname: Arisaka
authors.forename: Kin-ichiro
authors.initials: K
authors.lastname: Miura
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003224:Congo Red; D046529:Microscopy, Electron, Transmission; D008859:Microscopy, Polarization; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012965:Sodium Chloride / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014461:Ultracentrifugation
chemical_list: D010455:Peptides; D003224:Congo Red; D012965:Sodium Chloride
keywords: aggregation; amphipathic α-helix; fibrous assembly; self-assembly