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PH responsiveness of fibrous assemblies of repeat-sequence amphipathic ?-helix polypeptides.


ABSTRACT: We reported previously that our designed polypeptide ?3 (21 residues), which has three repeats of a seven-amino-acid sequence (LETLAKA)3, forms not only an amphipathic ?-helix structure but also long fibrous assemblies in aqueous solution. To address the relationship between the electrical states of the polypeptide and its ?-helix and fibrous assembly formation, we characterized mutated polypeptides in which charged amino acid residues of ?3 were replaced with Ser. We prepared the following polypeptides: 2S?3 (LSTLAKA)3, in which all Glu residues were replaced with Ser residues; 6S?3 (LETLASA)3, in which all Lys residues were replaced with Ser; and 2S6S?3 (LSTLASA)3; in which all Glu and Lys residues were replaced with Ser. In 0.1M KCl, 2S?3 formed an ?-helix under basic conditions and 6S?3 formed an ?-helix under acid conditions. In 1M KCl, they both formed ?-helices under a wide pH range. In addition, 2S?3 and 6S?3 formed fibrous assemblies under the same buffer conditions in which they formed ?-helices. ?-Helix and fibrous assembly formation by these polypeptides was reversible in a pH-dependent manner. In contrast, 2S6S?3 formed an ?-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 ?-helix formation.

SUBMITTER: Takei T 

PROVIDER: S-EPMC4420536 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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pH responsiveness of fibrous assemblies of repeat-sequence amphipathic α-helix polypeptides.

Takei Toshiaki T   Tsumoto Kouhei K   Okonogi Atsuhito A   Kimura Akiko A   Kojima Shuichi S   Yazaki Kazumori K   Takei Tsunetomo T   Ueda Takuya T   Miura Kin-ichiro K  

Protein science : a publication of the Protein Society 20150402 5


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 poly  ...[more]

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