PH responsiveness of fibrous assemblies of repeat-sequence amphipathic α-helix polypeptides

Toshiaki Takei*, Kouhei Tsumoto, Atsuhito Okonogi, Akiko Kimura, Shuichi Kojima, Kazumori Yazaki, Tsunetomo Takei, Takuya Ueda, Kin Ichiro Miura

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


We reported previously that our designed polypeptide α3 (21 residues), which has three repeats of a seven-amino-acid sequence (LETLAKA)3, forms not only an amphipathic α-helix structure but also long fibrous assemblies in aqueous solution. To address the relationship between the electrical states of the polypeptide and its α-helix and fibrous assembly formation, we characterized mutated polypeptides in which charged amino acid residues of α3 were replaced with Ser. We prepared the following polypeptides: 2Sα3 (LSTLAKA)3, in which all Glu residues were replaced with Ser residues; 6Sα3 (LETLASA)3, in which all Lys residues were replaced with Ser; and 2S6Sα3 (LSTLASA)3; in which all Glu and Lys residues were replaced with Ser. In 0.1M KCl, 2Sα3 formed an α-helix under basic conditions and 6Sα3 formed an α-helix under acid conditions. In 1M KCl, they both formed α-helices under a wide pH range. In addition, 2Sα3 and 6Sα3 formed fibrous assemblies under the same buffer conditions in which they formed α-helices. α-Helix and fibrous assembly formation by these polypeptides was reversible in a pH-dependent manner. In contrast, 2S6Sα3 formed an α-helix under basic conditions in 1M KCl. Taken together, these findings reveal that the charge states of the charged amino acid residues and the charge state of the Leu residue located at the terminus play an important role in α-helix formation.

Original languageEnglish
Pages (from-to)883-894
Number of pages12
JournalProtein Science
Issue number5
Publication statusPublished - 2015 May 1
Externally publishedYes


  • aggregation
  • amphipathic α-helix
  • fibrous assembly
  • pH responsiveness
  • self-assembly

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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