Characterization of amyloid protein AA and its serum precursor SAA in the horse.

This study examines the characteristics of amyloid protein AA and its precursor, serum amyloid A (SAA), in horses. The researchers identified and analyzed these proteins from an afflicted horse and found similar structural characteristics between horse and human AA proteins, though distinct species-related antigenic specificity was observed.

Study Procedure

• The research began with the extraction of amyloid from the liver of a horse suffering from amyloidosis. This condition developed after several years of the horse being used for antibodies production to fight bacterial antigens.
• The identified amyloid fibrils were classified as the AA, or Amyloid A, type.

Protein Characterization

• The research team then identified two AA proteins which had molecular weights of 9000 and 11,000.
• These proteins showed identical partial N-terminal amino acid sequences.

Homology and Specificity Observations

• They further analyzed the structure of the AA proteins and saw a distinct similarity in their structures with AA proteins from other species, including humans.
• Even though resemblance was observed, unique species-related antigenic specificity was also seen.

Serum Amyloid A (SAA)

• Serum amyloid A (SAA), the precursor to AA was studied as well. SAA was harvested from horse serum during the acute phase of septic abortion.
• The SAA was found to have identical antigenicity and initial 10 N-terminal amino acid residues characteristics as AA.
• Most of the SAA was present as part of the high-density lipoprotein complex in serum.
• SAA demonstrated heterogeneity in size, with most molecules having molecular weight of 11,000, and a minority having molecular weight of 9000.