Time-resolved FRET detection of subtle temperature-induced conformational biases in ensembles of α-synuclein molecules

Asaf Grupi, Elisha Haas

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18 Scopus citations

Abstract

The α-synuclein (αS) molecule, a polypeptide of 140 residues, is an intrinsically disordered protein that is involved in the onset of Parkinson's disease. We applied time-resolved excitation energy transfer measurements in search of specific deviations from the disordered state in segments of the αS backbone that might be involved in the initiation of aggregation. Since at higher temperatures, the αS molecule undergoes accelerated aggregation, we studied the temperature dependence of the distributions of intramolecular segmental end-to-end distances and their fast fluctuations in eight labeled chain segments of the αS molecule. Over the temperature range of 5-40°C, no temperature-induced unfolding or folding was detected at the N-terminal domain (residues 1-66) of the αS molecule. The intramolecular diffusion coefficient of the segments' ends relative to each other increased monotonously with temperature. A common very high upper limiting value of ∼ 25 A2/ns was reached at 40°C, another indication of a fully disordered state. Three exceptions were two segments with reduced values of the diffusion coefficients (the shortest segment where the excluded volume effect is dominant and the segment labeled in the NAC domain) and a nonlinear cooperative transition in the N-terminal segment. These specific subtle deviations from the common pattern of temperature dependence reflect specific structural constraints that could be critical in controlling the stability of the soluble monomer, or for its aggregation. Such very weak effects might be dominant in determination of the fate of ensembles of disordered polypeptides either to folding or to misfolding.

Original languageEnglish
Pages (from-to)234-247
Number of pages14
JournalJournal of Molecular Biology
Volume411
Issue number1
DOIs
StatePublished - 5 Aug 2011

Bibliographical note

Funding Information:
Plasmid encoding the WT αS was kindly provided by Dr Thomas Jovin of the Max Plank Institute for Biophysical Chemistry in Gottingen; his advice and encouragement are gratefully acknowledged. Ongoing discussions with Dan Amir, Gershon Hazan, and Maik H. Jacob contributed greatly to our study. This study was supported by grants from the German Israel Binational Science Foundation (GIF); the Israel Science Foundation (ISF1464/10); the EU Marie Curie TOK grant (29936), and by the Damadian Center for Magnetic Resonance Research, Bar-Ilan University.

Keywords

  • disordered protein
  • dynamics
  • folding
  • time-resolved FRET
  • α-synuclein

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