REDUCTION OF DISULFIDE BONDS IN AN AMYLOIDOGENIC JONES,BENCE PROTEIN LEADS TO FORMATION OF AMYLOID-LIKE FIBRILS IN-VITRO

Motivated by the finding that the amino acid sequence of the Bence Jones protein BJP-DIA was identical to that of the main protein component of the amyloid fibrils obtained from the same patient with AL-amyloidosis, (Klafki, H.-W., Kratzin, H-D., Pick, A.-I., Eckart, K., Karas, M. and Hilschmann, N. (1992) Biochemistry 31, 3265-3272.), we attempted to create ''amyloid-like'' fibrils from the Bence Jones protein in vitro, without addition of proteolytic enzymes. Reduction of BJP-DIA, solubilized in PBS, pH 7.4, overnight at 37 degrees C resulted in the formation of a precipitate which had affinity for the dye Congo red. Electron microscopy of negatively stained samples of the reduced protein revealed aggregates of linear unbranched fibrils. SDS-polyacrylamide gel electrophoresis demonstrated that the precipitate consisted almost exclusively of intact light chain molecules. This result makes it possible to deduce a molecular model of these amyloid fibrils generated in vitro.