Importance of micelle-like multimers in the atypical aggregation kinetics of N-terminal serum amyloid A peptides.

Amyloid formation occurs via numerous complex mechanisms, often involving intermediates. This study examines the mechanism of amyloidogenesis in two N-terminal fragments of serum amyloid A (SAA), which are known to exhibit dramatically different amyloid structures. Fibrillization kinetics by these peptides are found to exhibit two unusual features: slower rates at higher peptide concentration, and complete insensitivity to addition of pre-formed seed. Additionally, we find that these peptides form micelle-like oligomers in solution. Our results imply an unusual dual role of micellar oligomers in amyloidogenesis, in which these particles act both as an off-pathway reservoir of peptide, and an inhibitory aggregate that slows amyloid growth. We anticipate that this mechanism of fibril formation may exist in other hydrophobic amyloid-forming peptides and proteins. This article is protected by copyright. All rights reserved.