Murine apolipoprotein serum amyloid A in solution forms a hexamer containing a central channel

Limin Wang, Hilal A. Lashuel, Thomas Walz, Wilfredo Colón

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Serum amyloid A (SAA) is a small apolipoprotein that binds to high-density lipoproteins in the serum. Although SAA seems to play a role in host defense and lipid transport and metabolism, its specific functions have not been defined. Despite the growing implications that SAA plays a role in the pathology of various diseases, a high-resolution structure of SAA is lacking because of limited solubility in the high-density lipoprotein-free form. In this study, complementary methods including glutaraldehyde cross-linking, size-exclusion chromatography, and sedimentation-velocity analytical ultracentrifugation were used to show that murine SAA2.2 in aqueous solution exists in a monomer-hexamer equilibrium. Electron microscopy of hexameric SAA2.2 revealed that the subunits are arranged in a ring forming a putative central channel. Limited trypsin proteolysis and mass spectrometry analysis identified a significantly protease-resistant SAA2.2 region comprising residues 39-86. The isolated 39-86 SAA2.2 fragment did not hexamerize, suggesting that part of the N terminus is involved in SAA2.2 hexamer formation. Circular-dichroism spectrum deconvolution and secondary-structure prediction suggest that SAA2.2 contains ≈50% of its residues in α-helical conformation and <10% in β-structure. These findings are consistent with the recent discovery that human SAA1.1 forms a membrane channel and have important implications for understanding the 3D structure, multiple functions, and pathological roles of this highly conserved protein.

Original languageEnglish
Pages (from-to)15947-15952
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue number25
DOIs
Publication statusPublished - 10 Dec 2002
Externally publishedYes

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Serum Amyloid A Protein
Apolipoproteins
HDL Lipoproteins
Ultracentrifugation
Glutaral
Circular Dichroism
Ion Channels
Lipid Metabolism
Solubility
Trypsin
Proteolysis
Gel Chromatography
Mass Spectrometry
Electron Microscopy
Peptide Hydrolases
Pathology
Serum
Proteins

ASJC Scopus subject areas

  • Genetics
  • General

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Murine apolipoprotein serum amyloid A in solution forms a hexamer containing a central channel. / Wang, Limin; Lashuel, Hilal A.; Walz, Thomas; Colón, Wilfredo.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, No. 25, 10.12.2002, p. 15947-15952.

Research output: Contribution to journalArticle

Wang, Limin ; Lashuel, Hilal A. ; Walz, Thomas ; Colón, Wilfredo. / Murine apolipoprotein serum amyloid A in solution forms a hexamer containing a central channel. In: Proceedings of the National Academy of Sciences of the United States of America. 2002 ; Vol. 99, No. 25. pp. 15947-15952.
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