Amyloid fibrils were isolated from the kidney of a patient with Finnish hereditary amyloidosis. After solubilization of the fibrils in guanidine-HCl, fractionation by gel filtration, and purification by reverse-phase high-performance liquid chrornatography, a homogeneous amyloid protein with an apparent M r of 9000 was obtained. The protein was subjected to enzymatic digestion by trypsin and endoproteinase Lys-C. The amino acid sequences were determined for 6 of the released peptides and they were all found to be identical to the reported, deduced primary structure of human plasma gelsoline in the region of amino acids 235–269. The results show that the amyloid fibril protein in Finnish hereditary amyloidosis represents a new type of amyloid protein that shows amino acid sequence homology with gelsoline, an actin-modulating protein.
