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Structure of serum amyloid A suggests a mechanism for selective lipoprotein binding and functions: SAA as a hub in macromolecular interaction networks.

ABSTRACT: Serum amyloid A is a major acute-phase plasma protein that modulates innate immunity and cholesterol homeostasis. We combine sequence analysis with x-ray crystal structures to postulate that SAA acts as an intrinsically disordered hub mediating interactions among proteins, lipids and proteoglycans. A structural model of lipoprotein-bound SAA monomer is proposed wherein two ?-helices from the N-domain form a concave hydrophobic surface that binds lipoproteins. A C-domain, connected to the N-domain via a flexible linker, binds polar/charged ligands including cell receptors, bridging them with lipoproteins and rerouting cholesterol transport. Our model is supported by the SAA cleavage in the interdomain linker to generate the 1-76 fragment deposited in reactive amyloidosis. This model sheds new light on functions of this enigmatic protein.

SUBMITTER: Frame NM

PROVIDER: S-EPMC4805461 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Structure of serum amyloid A suggests a mechanism for selective lipoprotein binding and functions: SAA as a hub in macromolecular interaction networks.

Frame Nicholas M NM Gursky Olga O

FEBS letters 20160306 6

Serum amyloid A is a major acute-phase plasma protein that modulates innate immunity and cholesterol homeostasis. We combine sequence analysis with x-ray crystal structures to postulate that SAA acts as an intrinsically disordered hub mediating interactions among proteins, lipids and proteoglycans. A structural model of lipoprotein-bound SAA monomer is proposed wherein two α-helices from the N-domain form a concave hydrophobic surface that binds lipoproteins. A C-domain, connected to the N-domai ...[more]

PMID: 26918388

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