The Complete Primary Structure of Bovine Serum Amyloid Protein a (SAA) and of Tissue Amyloid Fibril Protein a (AA) Subspecies

The goal of this work was to determine the complete covalent structures of the bovine proteins SAA and AA. Protein AA was isolated from the amyloid fibrils extracted from the kidneys. Three molecular species of protein AA was characterised and were found to consist of 68, 81 and about 112 amino acid residues, respectively. The protein SAA isolated from acute phase HDL was composed of 112 amino acid residues. The amino acid sequence elucidated for the protein AA subspecies was identical to that determined for protein SAA. No microheterogeneity could be detected in the amino acid sequence of protein SAA or of protein AA subspecies. The data thus suggest the existence of only one molecular species of protein SAA and that this species is amyloidogenic. As shown for the equine protein SAA, an insertion of several amino acid residues between positions 68 and 69 could be established.