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Aggregation of partially unfolded Myosin subfragment-1 into spherical oligomers with amyloid-like dye-binding

Hideyuki Komatsu1, Nami Shinotani, Yoshitaka Kimori

  • 1Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Iizuka, Fukuoka, 820-8502. hide@bio.kyutech.ac.jp

Journal of Biochemistry
|June 22, 2006
PubMed

Insights

Mild heat causes myosin subfragment 1 (S1) to partially unfold and aggregate into amyloid-like spherical particles, not amorphous masses. These S1 aggregates may influence protein assembly and morphology.

Area of Science:

  • Biochemistry
  • Protein aggregation
  • Structural biology

Background:

  • Proteolytic myosin subfragment 1 (S1) undergoes partial unfolding in its 50-kDa subdomain upon mild heat treatment (35°C).
  • Understanding the aggregation behavior of partially unfolded proteins is crucial for comprehending cellular processes and disease mechanisms.

Purpose of the Study:

  • To investigate the aggregation characteristics of partially unfolded myosin subfragment 1 (S1) induced by mild heat.
  • To determine the morphology and properties of the resulting S1 aggregates.

Main Methods:

  • Mild heat treatment of S1 protein at 35°C.
  • Ultracentrifugation to isolate aggregates.
  • Congo red binding and Thioflavin T fluorescence assays to assess amyloid-like properties.
  • Electron microscopy for morphological analysis.
  • Gel filtration to study the aggregation pathway.
  • Tryptic digestion to evaluate aggregate stability.

Main Results:

  • Partial unfolding of S1 at 35°C induced aggregation into spherical particles.
  • Aggregates exhibited amyloid-like properties, including Congo red binding and Thioflavin T fluorescence.
  • Electron microscopy revealed uniformly sized spherical particles, distinct from amorphous aggregates.
  • Gel filtration indicated an intermediate oligomeric stage during spheroid formation.
  • The S1 aggregate inhibited the aggregation of an isolated 50-kDa fragment.

Conclusions:

  • Partially unfolded S1 molecules assemble into spherical, amyloid-like particles rather than amorphous masses.
  • The native regions within partially unfolded S1 likely dictate the specific morphology of the aggregates.
  • These findings suggest that protein structure and residual native regions play a key role in determining aggregate form.

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