Epigallocatechin-3-gallate Inhibits Cu(II)-Induced ß-2-Microglobulin Amyloid Formation by Binding to the Edge of Its ß-Sheets.

Epigallocatechin-3-gallate (EGCG) is a catechin found in green tea that can inhibit the amyloid formation of a wide variety of proteins. EGCG's ability to prevent or redirect the amyloid formation of so many proteins may reflect a common mechanism of action, and thus, greater molecular-level insight into how it exerts its effect could have broad implications. Here, we investigate the molecular details of EGCG's inhibition of the protein ß-2-microglobulin (ß2m), which forms amyloids in patients undergoing long-term dialysis treatment. Using size-exclusion chromatography and a collection of mass spectrometry-based techniques, we find that EGCG prevents Cu(II)-induced ß2m amyloid formation by diverting the normal progression of preamyloid oligomers toward the formation of spherical, redissolvable aggregates. EGCG exerts its effect by binding with a micromolar affinity (Kd ≈ 5 µM) to the ß2m monomer on the edge of two ß-sheets near the N-terminus. This interaction destabilizes the preamyloid dimer and prevents the formation of a tetramer species previously shown to be essential for Cu(II)-induced ß2m amyloid formation. EGCG's binding at the edge of the ß-sheets in ß2m is consistent with a previous hypothesis that EGCG generally prevents amyloid formation by binding cross-ß-sheet aggregation intermediates.