IR spectroscopic analyses of amyloid fibril formation of beta 2-microglobulin using a simplified procedure for its in vitro generation at neutral pH

Beta 2-microglobulin (beta 2m) is known to be the major component of fibrillar deposits in the joints of patients suffering from dialysis-related amyloidosis. We have developed a simplified procedure to convert monomeric recombinant beta 2m into amyloid fibrils at physiological pH by a combination of stirring and heating, enabling us to follow conformational changes associated with the assembly by infrared spectroscopy and electron microscopy. Our studies reveal that fibrillogenesis begins with the formation of relatively large aggregates, with secondary structure not significantly altered by the stirring-induced association. In contrast, the conversion of the amorphous aggregates into amyloid fibrils is associated with a profound re-organization at the level of the secondary and tertiary structures, leading to non-native like parallel arrangements of the beta-strands in the fully formed amyloid structure of beta 2m. This study highlights the power of an approach to investigate the formation of beta 2m fibrils by a combination of biophysical techniques including IR spectroscopy.