Structural evidence for asymmetric ligand binding to transthyretin

Michele Cianci1, Claudia Folli2, Francesco Zonta3

  • 1EMBL Hamburg Outstation, c/o DESY, Building 25a, Notkestrasse 85, 22603 Hamburg, Germany.

Insights

Researchers discovered that transthyretin (TTR) has asymmetric binding sites for drugs, a finding that could lead to new combination therapies for TTR amyloidosis by targeting distinct sites.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Pharmacology

Background:

  • Transthyretin (TTR) is an amyloidogenic protein implicated in TTR amyloidosis.
  • Stabilizing TTR's native state is a therapeutic strategy for TTR amyloidosis.
  • TTR possesses two thyroxine (T4) binding sites with negative binding cooperativity.

Purpose of the Study:

  • To investigate the binding characteristics of natural polyphenols to TTR.
  • To understand the structural basis of asymmetric ligand binding to TTR.
  • To explore the therapeutic potential of TTR binding asymmetry.

Main Methods:

  • X-ray crystallography was used to determine the structures of TTR complexed with pterostilbene, quercetin, and apigenin.
  • Structural analysis was performed to identify differences between the two T4 binding sites.
  • Molecular-dynamics simulations and competition binding assays were conducted to study binding in solution.

Main Results:

  • Natural polyphenols (pterostilbene, quercetin) showed preferential binding to one TTR site, with lower occupancy in the second site.
  • Structural analysis revealed subtle conformational differences between the two T4 binding sites.
  • Molecular dynamics suggested more pronounced differences in solution, and competition assays confirmed distinct binding preferences for polyphenols versus T4.

Conclusions:

  • TTR exhibits significant binding asymmetry for natural polyphenols and T4.
  • This asymmetry is characterized by distinct binding affinities and site preferences.
  • Exploiting this TTR binding asymmetry with combination drug therapy could enhance protein stabilization and treat TTR amyloidosis.

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