Effect of amino acid variations in the central region of human serum amyloid A on the amyloidogenic properties.
Human serum amyloid A (SAA) is a precursor protein of the amyloid fibrils that are responsible for AA amyloidosis. Of the four human SAA genotypes, SAA1 is most commonly associated with AA amyloidosis. Furthermore, SAA1 has three major isoforms (SAA1.1, 1.3, and 1.5) that differ by single amino acid variations at two sites in their 104-amino acid sequences. In the present study, we examined the effect of amino acid variations in human SAA1 isoforms on the amyloidogenic properties. All SAA1 isoforms adopted α-helix structures at 4°C, but were unstructured at 37°C. Heparin-induced amyloid fibril formation of SAA1 was observed at 37°C, as evidenced by the increased thioflavin T (ThT) fluorescence and β-sheet structure formation. Despite a comparable increase in ThT fluorescence, SAA1 molecules retained their α-helix structures at 4°C. At both temperatures, no essential differences in ThT fluorescence and secondary structures were observed among the SAA1 isoforms. However, the fibril morphologies appeared to differ; SAA1.1 formed long and curly fibrils, whereas SAA1.3 formed thin and straight fibrils. The peptides corresponding to the central regions of the SAA1 isoforms containing amino acid variations showed distinct amyloidogenicities, reflecting their direct effects on amyloid fibril formation. These findings may provide novel insights into the influence of amino acid variations in human SAA on the pathogenesis of AA amyloidosis.
Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan.
Hiroka
H
Takase
Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan. Electronic address: masatnk@kobepharma-u.ac.jp.
Masafumi
M
Tanaka
Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan.
Sachiko
S
Miyagawa
Department of Clinical Laboratory Medicine, Jichi Medical University, Shimotsuke 329-0498, Japan.
Toshiyuki
T
Yamada
Department of Biophysical Chemistry, Kobe Pharmaceutical University, Kobe 658-8558, Japan.
Takahiro
T
Mukai
D058227:Amyloidogenic Proteins / Q000097:blood* / Q000737:chemistry / Q000235:genetics*; D000686:Amyloidosis / Q000097:blood / Q000209:etiology / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D046529:Microscopy, Electron, Transmission; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000097:blood / Q000737:chemistry / Q000235:genetics; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000685:Serum Amyloid A Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D058227:Amyloidogenic Proteins; D010446:Peptide Fragments; D020033:Protein Isoforms; D011994:Recombinant Proteins; C521404:SAA1 protein, human; D000685:Serum Amyloid A Protein
Amino acid variation; Amyloid fibril formation; Fibril morphology; Serum amyloid A; Synthetic fragment peptide