Hexapeptide Tandem Repeats Dictate the Formation of Silkmoth Chorion, a Natural Protective Amyloid

J Mol Biol. 2018 Oct 12;430(20):3774-3783. doi: 10.1016/j.jmb.2018.06.042. Epub 2018 Jun 28.

Abstract

Silkmoth chorion is a fibrous structure composed mainly of two major protein classes, families A and B. Both families of silkmoth chorion proteins present a highly conserved, in sequence and in length, central domain, consisting of Gly-rich tandem hexapeptide repetitive segments, flanked by two more variable N-terminal and C-terminal arms. Primary studies identified silkmoth chorion as a functional protective amyloid by unveiling the amyloidogenic properties of the central domain of both protein families. In this work, we attempt to detect the principal source of amyloidogenicity of the central domain by focusing on the role of the tandem hexapeptide sequence repeats. Concurrently, we discuss a possible mechanism for the self-assembly of class A protofilaments, suggesting that the aggregation-prone hexapeptide building blocks may fold into a triangle-shaped β-helical structure.

Keywords: functional amyloids; silkmoth chorion proteins; silkmoth eggshell; tandem repeats.

MeSH terms

  • Amino Acid Sequence
  • Amyloid / chemistry*
  • Amyloid / metabolism*
  • Amyloidogenic Proteins / chemistry
  • Amyloidogenic Proteins / metabolism
  • Animals
  • Bombyx / metabolism*
  • Chorion / chemistry*
  • Chorion / metabolism*
  • Insect Proteins / chemistry
  • Insect Proteins / metabolism
  • Models, Molecular
  • Oligopeptides / chemistry*
  • Oligopeptides / metabolism*
  • Protein Aggregates
  • Protein Aggregation, Pathological
  • Protein Conformation
  • Spectrum Analysis
  • Tandem Repeat Sequences*

Substances

  • Amyloid
  • Amyloidogenic Proteins
  • Insect Proteins
  • Oligopeptides
  • Protein Aggregates