Physical and Chemical Properties of Amyloid Fibers Ii. Isolation of a Unique Protein Constituting the Major Component From Human Splenic Amyloid Fibril Concentrates

A major protein component (B protein) obtained from concentrated fibrils of each of two human amyloidotic spleens has been isolated by a series of fractionation methods using extraction in buffered 8 M urea, complete denaturation in buffered 6 M guanidine and column chromatography on Sepharose 4 B (Pharmacia). The major protein obtained by column chromatography was found to be also the major protein component on sodium dodecyl sulfate polyacrylamide disc electrophoresis. This protein was shown to have a molecular weight of 21,000-22,500. Immunologic identity was demonstrated for the B protein derived from the amyloid fibril concentrates of each spleen. No evidence of antibody cross-reaction to native or denatured components of normal human spleen or serum was discernible. It would appear, therefore, that the B protein derived from the two splenic amyloid fibril preparations, in addition to being the major protein component of the fibril, is not found in significant quantity in normal tissue or serum.