Structural convergence among diverse, toxic beta-sheet ion channels.

Area of Science:

• Biophysics
• Molecular Biology
• Biochemistry

Background:

• Beta-sheet peptides, including truncated amyloid-beta (Abeta) and K3 fragments, form ion channels in lipid bilayers.
• These peptide-formed ion channels induce cell damage via calcium overload.
• Despite sequence diversity, these toxic channels exhibit similar dimensions, raising questions about preferred sizes.

Purpose of the Study:

• To investigate the preferred channel sizes of toxic beta-sheet peptide ion channels.
• To model truncated Abeta peptide (p3) channels using ssNMR-based coordinates.
• To determine the optimal oligomerization states for toxic ion flux.

Main Methods:

• Utilized ssNMR-based U-shaped, beta-strand-turn-beta-strand coordinates for modeling.
• Performed molecular dynamics (MD) simulations on modeled p3 channels (12- to 36-mer).
• Compared simulation results with atomic force microscopy (AFM) data of Abeta(9-42), K3, and PG-1 channels.

Main Results:

• MD simulations identified optimal ion channel sizes for toxic ionic flux between 16- and 24-mers.
• These findings align with AFM-imaged channel dimensions for various toxic peptides.
• The study highlights preferred sizes and organization of toxic beta-channels in lipid bilayers.

Conclusions:

• The size of toxic beta-sheet peptide ion channels is a critical factor in their function and toxicity.
• A preferred range of 16- to 24-mers optimizes ion flux and cell damage.
• These findings suggest a conserved mechanism for beta-sheet peptide channel formation and toxicity, irrespective of specific amino acid sequences.