Effect of electrostatics on aggregation of prion protein Sup35 peptide

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23 Scopus citations

Abstract

Self-assembly of misfolded proteins into ordered fibrillar structures is a fundamental property of a wide range of proteins and peptides. This property is also linked with the development of various neurodegenerative diseases such as Alzheimers and Parkinsons. Environmental conditions modulate the misfolding and aggregation processes. We used a peptide, CGNNQQNY, from yeast prion protein Sup35, as a model system to address effects of environmental conditions on aggregate formation. The GNNQQNY peptide self-assembles in fibrils with structural features that are similar to amyloidogenic proteins. Atomic force microscopy (AFM) and thioflavin T (ThT) fluorescence assay were employed to follow the aggregation process at various pHs and ionic strengths. We also used single molecule AFM force spectroscopy to probe interactions between the peptides under various conditions. The ThT fluorescence data showed that the peptide aggregates fast at pH values approaching the peptide isoelectric point (pI=5.3) and the kinetics is 10 times slower at acidic pH (pH 2.0), suggesting that electrostatic interactions contribute to the peptide self-assembly into aggregates. This hypothesis was tested by experiments performed at low (11mM) and high (150mM) ionic strengths. Indeed, the aggregation lag time measured at pH 2 at low ionic strength (11mM) is 195h, whereas the lag time decreases 5 times when the ionic strength is increased to 150mM. At conditions close to the pI value, pH 5.6, the aggregation lag time is 12±6h under low ionic strength, and there is minimal change to the lag time at 150mM NaCl. The ionic strength also influences the morphology of aggregates visualized with AFM. In pH 2.0 and at high ionic strength, the aggregates are twofold taller than those formed at low ionic strength. In parallel, AFM force spectroscopy studies revealed minimal contribution of electrostatics to dissociation of transient peptide dimers.

Original languageEnglish (US)
Article number164205
JournalJournal of Physics Condensed Matter
Volume24
Issue number16
DOIs
StatePublished - Apr 25 2012

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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