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Fibril formation from recombinant human serum amyloid A
T Yamada1, B Kluve-Beckerman, J J Liepnieks
1Department of Medicine, Indiana University School of Medicine, Indianapolis.
Biochimica Et Biophysica Acta
|July 18, 1994
Summary
Human serum amyloid A (SAA) protein isotypes were expressed in E. coli. SAA1 demonstrated a higher potential for forming amyloid fibrils compared to SAA2 beta and SAA4.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Chemistry
Background:
- Serum amyloid A (SAA) proteins are acute-phase reactants involved in inflammation.
- Three major human SAA isotypes (SAA1, SAA2 beta, SAA4) are known, but their fibril-forming potentials differ.
- Understanding SAA isotype-specific amyloidogenesis is crucial for comprehending amyloid diseases.
Purpose of the Study:
- To express and purify recombinant human SAA isotypes (SAA1, SAA2 beta, SAA4) in Escherichia coli (E. coli).
- To investigate the in vitro fibril-forming capabilities of purified SAA isotypes.
- To compare the amyloidogenic potential of SAA1, SAA2 beta, and SAA4.
Main Methods:
- Recombinant SAA (rSAA) isotypes were expressed in E. coli using the pET vector system.
- Purification involved molecular sieve chromatography, chromatofocusing, and hydrophobic interaction chromatography.
- Amyloid fibril formation was assessed using Congo red staining and electron microscopy.
Main Results:
- High yields (5-10 mg/L) of purified rSAA isotypes were obtained.
- rSAA1 formed amyloid-like fibrils under in vitro conditions, confirmed by Congo red staining and electron microscopy.
- rSAA2 beta and SAA4 showed negative Congo red staining and formed non-amyloid fibrillar structures.
Conclusions:
- SAA1 exhibits a significantly greater propensity for amyloid fibril formation compared to SAA2 beta and SAA4.
- These findings highlight isotype-specific differences in SAA amyloidogenesis.
- SAA1 may play a more prominent role in the pathogenesis of SAA-related amyloidosis.