G T Westermark — Page 3

PubMed1987

Amyloid fibril protein AA. Characterization of uncommon subspecies from a patient with rheumatoid arthritis.

Protein AA, the main fibril protein in secondary systemic amyloidosis, is a mixture of protein fragments (subspecies) of different length, probably arising by enzymatic cleavage of a serum precursor, SAA. We have purified amyloid fibril protein AA from a patient with rheumatoid arthritis and secondary amyloidosis with an unusual amyloid distribution in organs. This protein AA contained two major subspecies of which one consisted of 50 amino acid residues shown by complete amino acid sequence analysis. The other major AA subspecies, characterized by N- and C-terminal sequence analysis and amino acid determination of proteolytic peptides, contained 45 amino acid residues. The pI of these AA-variants differed considerably, 8.1 to 5.5, respectively. Several minor protein AA subspecies were also identified, among them one with a blocked N-terminal. The findings indicate that AA proteins of different length are connected to varying AA amyloid syndromes.

Amino Acid Sequence↗

PubMed1986

Bovine amyloid protein AA: isolation and amino acid sequence analysis.

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.

Amino Acid Sequence↗