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serum amyloid P component; 9.5S alpha-1 glycoprotein (SAP)
A pentraxin or pentaxin
Function:
- major DNA & chromatin-binding protein of plasma
- may scavenge nuclear material released from damaged circulating cells
- may serve as Ca+2-dependent lectin
- binds fibronectin, C4-binding protein & glycosaminoglycans
- binding to all of these ligands is Ca+2-dependent
- SAP is a normal tissue matrix constituent associated with elastic fibers & the glomerular basement membrane.
Structure:
- N-glycosylated with a complex biantennary oligosaccharide chain with a sialic acid at the end (disialo-SAP). monosialo- SAP as well as asioalo-SAP are also detected
- circulates as dimer of pentamers
- more than 50% sequence homology with C-reactive protein
Compartment: secreted
Expression: found in serum & urine
Pathology:
- SAP binds to all forms of amyloid fibrils & is present in all amyloid desposits including amyloid of basement membrane & amyloid plaques of Alzheimer's disease
- radio-labeled SAP is used as a specific quantitative in vivo tracer for amyloid deposits
Laboratory:
- amyloid P component Ag in tissue
General
acute phase protein
amyloid
pentraxin-2 (neuronal pentraxin, NPTX)
Properties
CONFIGURATION: pentamer
SIZE: entity length = 204 aa
COMPARTMENT: plasma
MOTIF: Ca+2-binding site (2)
MOTIF: aspartate residue {D58}
asparagine residue {N59}
glutamate residue {E136}
glutamine residue {Q137}
aspartate residue {D138}
glutamine residue {Q148}
glycosylation site
binding site
FOR-BINDING-OF: amyloid
deoxyribonucleic acid (DNA)
heparan sulfate
dermatan sulfate
fibronectin
binding site
FOR-BINDING-OF: phosphatidylethanolamine
Database Correlations
OMIM 104770
UniProt P02743
Entrez Gene 325
References
- Emsley J et al
Structure of pentameric human serum amyloid P component.
Nature 367:338 1994
PMID: 8114934
- Bodin K et al.
Antibodies to human serum amyloid P component eliminate
visceral amyloid deposits.
Nature 2010 Nov 4; 468:93.
PMID: 20962779
- UniProt :accession P02743
- Wikipedia; Note: serum amyloid P component entry
http://en.wikipedia.org/wiki/serum_amyloid_P_component