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Protein AA was purified from the kidneys of dogs with spontaneous reactive amyloidosis. The protein had a blocked N-terminal. Sequence analysis of a peptide obtained after cyanogen bromide cleavage revealed an amino acid sequence corresponding to positions 24-42 of human AA. This region showed a strong homology to protein AA of other species. Antiserum to both human and dog protein AA reacted immunohistochemically with AA amyloid of human, dog and cow origin.

1. Amyloid isolated from the liver of a domestic short-haired (DSH) cat was dissolved and purified by gel filtration for amino acid sequence analysis. 2. Sequences of two major peptides corresponding to positions 18-23 and 25-75 of human amyloid protein AA were obtained when cyanogen bromide-cleaved protein was applied to an amino acid sequenator. 3. Comparison of these regions of amyloid protein from the Abyssinian cat (high incidence of AA amyloidosis) and DSH cat (low incidence of AA amyloidosis) revealed three amino acid differences, two of which occurred within regions that are completely conserved in the Abyssinian cat and all other species. 4. Secondary prediction plots showed less potential for amyloidogenicity (i.e., less beta-sheet conformation) in protein AA of the DSH cat as compared to the Abyssinian cat and other animal species. 5. These differences in protein AA of the DSH cat may, therefore, be linked to the comparatively uncommon occurrence of AA amyloidosis in the DSH cat as compared to the Abyssinian cat and other animals species.

Amyloid-laden renal glomeruli were selectively isolated from a cow with a history of multiple organ inflammatory diseases which terminated in amyloid-induced glomerulopathy and severe proteinuria. Lyophilized amyloid fibrils obtained by water extraction procedures were dissolved in 6M guanidine hydrochloride and gel filtered on Sepharose CL6B and Sephacryl S-300 Superfine columns for slab gel electrophoresis, analytic isoelectric focusing, and amino acid sequence analyses. Electrophoresis of material from the major retarded peak of the elution profile revealed that bovine protein AA moves as one band with an apparent molecular mass of about 14,000 Daltons. Several distinct bands between approximately pH 4.0 and 5.0 were observed when this material was evaluated by analytic isoelectric focusing, thus having a pattern resembling that of human and dog protein AA. A blocked N-terminus was demonstrated when protein from the major retarded peak was subjected to amino acid sequencing, but cyanogen bromide cleavage followed by gel filtration produced 3 peptide fragments for amino acid sequence analysis. These peptides had a high degree of homology with positions 4-14, 18-24 and 25-49 of human protein AA. An apparent complete homology between bovine protein AA and protein AA from other species was apparent at positions 35-45, providing further evidence that this is a functionally significant part of the serum protein AA (SAA) molecule.