title: Sensitive and selective detection of free FXIII activation peptide: a potential marker of acute thrombotic events.
abstract: Coagulation factor XIII (FXIII) stabilizes fibrin fibers and is therefore a major player in the maintenance of hemostasis. FXIII is activated by thrombin resulting in cleavage and release of the FXIII activation peptide (AP-FXIII). The objective of this study was to characterize the released AP-FXIII and determine specific features that may be used for its specific detection. We analyzed the structure of bound AP-FXIII within the FXIII A-subunit and interactions of AP-FXIII by hydrogen bonds with both FXIII A-subunit monomers. We optimized our previously developed AP-FXIII ELISA by using 2 monoclonal antibodies. We determined high binding affinities between the antibodies and free AP-FXIII and demonstrated specific binding by epitope mapping analyses with surface plasmon resonance and enzyme-linked immunosorbent assay. Because the structure of free AP-FXIII had been characterized so far by molecular modeling only, we performed structural analysis by nuclear magnetic resonance. Recombinant AP-FXIII was largely flexible both in plasma and water, differing significantly from the rigid structure in the bound state. We suggest that the recognized epitope is either occluded in the noncleaved form or possesses a structure that does not allow binding to the antibodies. On the basis of our findings, we propose AP-FXIII as a possible new marker for acute thrombotic events.
authors.affiliation: Department of Hematology, Hemostasis Research Laboratory, University Hospital Bern, Inselspital, Bern, Switzerland.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Ortner
authors.forename: Verena
authors.initials: V
authors.lastname: Schroeder
authors.forename: Reto
authors.initials: R
authors.lastname: Walser
authors.forename: Oliver
authors.initials: O
authors.lastname: Zerbe
authors.forename: Hans P
authors.initials: HP
authors.lastname: Kohler
mesh_terms: D000208:Acute Disease; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D001665:Binding Sites; D015415:Biomarkers / Q000097:blood*; D002942:Circular Dichroism; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D005176:Factor XIII / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000097:blood* / Q000737:chemistry / Q000276:immunology*; D021122:Protein Subunits; D020349:Surface Plasmon Resonance; D013927:Thrombosis / Q000097:blood / Q000175:diagnosis / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D021122:Protein Subunits; C061895:factor XIII activation peptide; D005176:Factor XIII