Serum amyloid P component

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Amyloid P component, serum
Cartoon model of SAP showing helices in red, sheets in yellow and coils in green.
Identifiers
Symbol(s)	APCS; MGC88159; PTX2; SAP
External IDs	OMIM: 104770 MGI: 98229 Homologene: 1239
Gene ontology Molecular Function: • calcium ion binding • sugar binding • unfolded protein binding Cellular Component: • extracellular region • extracellular space Biological Process: • protein folding • acute-phase response • chaperone-mediated protein complex assembly
RNA expression pattern
More reference expression data
Orthologs
	Human	Mouse
Entrez	325	20219
Ensembl	ENSG00000132703	ENSMUSG00000026542
Uniprot	P02743	Q4JFI8
Refseq	NM_001639 (mRNA) NP_001630 (protein)	NM_011318 (mRNA) NP_035448 (protein)
Location	Chr 1: 157.82 - 157.83 Mb	Chr 1: 174.73 - 174.73 Mb
Pubmed search	[1]	[2]

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Overview

Amyloid P component, serum (SAP) is the identical serum form of amyloid P component (AP), a 25kDa pentameric protein first identified as the pentagonal constituent of in vivo pathological deposits called "amyloid".^[1]. APCS is its human gene.^[1]

In amyloidosis

AP makes up 14% of the dry mass of amyloid deposits^[1] and is thought to be an important contributor to the pathogenesis of a related group of diseases called the Amyloidoses.^[1] These conditions are characterised by the ordered aggregation of normal globular proteins and peptides into insoluble fibres which disrupt tissue architecture and are associated with cell death. AP is thought to decorate and stabilise aggregates by preventing proteolytic cleavage and hence inhibiting fibril removal via the normal protein scavenging mechanisms.^[1] This association is utilised in the routine clinical diagnostic technique of SAP scintigraphy whereby radio-labelled protein is injected into patients to locate areas of amyloid deposition.^[1] The SAP-amyloid association has also been identified as a possible drug target for anti-amyloid therapy, with the recent development and first stage clinical trials of a compound called CPHPC (R-1-[6-[R-2-carboxy-pyrrolidin-1-yl]-6-oxohexanoyl] pyrrolidine-2-carboxylic acid), a small molecule able to strip AP from deposits by reducing levels of circulating SAP.^[1]

Structure

SAP is a member of the pentraxins family, characterised by calcium dependent ligand binding and distinctive flattened β-jellyroll structure similar to that of the legume lectins.^[1] The name "pentraxin" is derived from the Greek word for five (penta) and berries (ragos) relating to the radial symmetry of five monomers forming a ring approximately 95 Å across and 35 Å deep. Human SAP has 51% sequence homology with C-reactive protein (CRP), a classical acute phase response plasma protein, and is a more distant relative to the "long" pentraxins such as PTX3 (a cytokine modulated molecule) and several neuronal pentraxins. Both SAP and CRP are evolutionary conserved in all vertebrates and also found in distant invertebrates such as the horse-shoe crab (Limulus polyphemus).^[1]

References

v • d • e Protein: glycoproteins

Activin - ADAM protein - Alpha 1-antichymotrypsin - Apolipoprotein H - CD70 - Asialoglycoprotein - Avidin - B-cell activating factor - 4-1BB ligand - Cholesterylester transfer protein - Clusterin - Colony-stimulating factor - Haemopexin - Inhibin - Lactoferrin - Membrane glycoproteins - Mucoprotein - Myelin protein zero - Osteonectin - Protein C - Protein S - Proteoglycan - Serum Amyloid P component - Sialoglycoprotein (CD43, Glycophorin, Glycophorin C) - Thrombopoietin - Thyroglobulin - Thyroxine-binding proteins - Transcortin - Tumor necrosis factor-alpha - Uteroglobin - Vitronectin

v • d • e Acute phase proteins
Alpha 1-antichymotrypsin - Alpha 1-antitrypsin - Alpha 2-macroglobulin - C-reactive protein - Ceruloplasmin - C3 - Fibrin - Haptoglobin - Haemopexin - Orosomucoid - Serum albumin (negative) - Amyloid (P, A) - Transferrin

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Acknowledgement and Attribution Regarding Sources of Content

Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .