title: Investigating interactions of the pentraxins serum amyloid P component and C-reactive protein by mass spectrometry.
abstract: The oligomeric state of human SAP (serum amyloid P component) in the absence and presence of known ligands has been investigated using nanoelectrospray ionization MS. At pH 8.0, in the absence of Ca2+, SAP has been shown to consist of pentameric and decameric forms. In the presence of physiological levels of Ca2+, SAP was observed to exist primarily as a pentamer, reflecting its in vivo state. dAMP was shown not only to promote decamerization, but also to lead to decamer stacking involving up to 30 monomers. A mechanism for this finding is proposed. CRP (C-reactive protein), a pentraxin closely related to SAP, exists as a pentamer in the presence or absence of Ca2+. Pentamers of CRP and SAP were shown to form mixed decamers in Ca2+-free buffer; however, in the presence of Ca2+, this interaction was not observed. Furthermore, no exchange of monomeric subunits was observed between the SAP and CRP oligomers, suggesting a remarkable stability of the individual pentameric complexes.
authors.affiliation: Department of Chemistry, Cambridge University, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Aquilina
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
mesh_terms: D002097:C-Reactive Protein / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000737:chemistry / Q000494:pharmacology; D019281:Dimerization; D006801:Humans; D008024:Ligands; D011485:Protein Binding / Q000187:drug effects; D000683:Serum Amyloid P-Component / Q000737:chemistry* / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D008024:Ligands; D000683:Serum Amyloid P-Component; D002097:C-Reactive Protein; D002118:Calcium