The covalent structure of amyloid-related serum protein SAA from two patients with inflammatory disease.

The complete covalent structure of an amyloid-related serum protein SAA from a patient (Jen.) with severe rheumatoid arthritis, is presented. The structure was elucidated by N-terminal analyses of the protein as well as on peptides derived from tryptic digestion and after cleaving the protein with BNPS-skatole. The characterization of tryptic peptide T-9 revealed a polymorphism similar to that seen in protein AA. Structural studies performed on another protein SAA, isolated from a patient (Mik.) with acute systemic lupus erythematosus, indicated that this protein is homologous to that from patient Jen. The formation and deposition of the protein AA-containing amyloid fibrils is discussed.