Influence of sulphate ions on the structure of AA amyloid fibrils

To explore the possible interaction of sulphated GAG with AA amyloid peptides, human AA amyloid fibrils were exposed to buffers containing various salts, and the accessibility of free amino groups on the peptides to reductive methylation was examined. Sodium chloride had little effect except at concentrations of 1 M, where it reduced the accessibility of AA peptides to labelling. In contrast 70 mM Na2SO4 led to a significant increase in peptide accessibility to labelling. The results suggest that, at least in part, GAG interact with AA peptides through their sulphate moieties.