A novel amyloid fibril protein isolated from senescence-accelerated mice.

A protein was isolated from amyloid fibrils extracted from the liver of an inbred strain of mice (senescence-accelerated mouse) characterized by a high frequency of age-associated systemic amyloidosis. This 5200-dalton protein has a different electrophoretic mobility from the murine protein AA. Its amino acid composition also differs from that of murine protein AA and from the amyloid protein in SJL/J, the only strain for which the spontaneous occurring amyloid has been characterized biochemically and immunochemically. Sequence analysis of the protein also revealed a blocked N-terminus. Immunochemically, the protein did not react with antisera against mouse immunoglobulin components. The antiserum against the protein did not react with murine protein AA, mouse immunoglobulin components, or with mouse normal liver protein. Thus, we have characterized an amyloid protein that is distinguishable from previously reported murine amyloid proteins and is not related to immunoglobulins. The possible relationship between this protein, designated ASSAM, and ASc in human senile cardiac amyloidosis is considered.