title: The interaction between fibrinogen and zymogen FXIII-A2B2 is mediated by fibrinogen residues γ390-396 and the FXIII-B subunits.
abstract: Coagulation transglutaminase factor XIII (FXIII) exists in circulation as heterotetrameric proenzyme FXIII-A2B2Effectively all FXIII-A2B2circulates bound to fibrinogen, and excess FXIII-B2circulates in plasma. The motifs that mediate interaction of FXIII-A2B2with fibrinogen have been elusive. We recently detected reduced binding of FXIII-A2B2to murine fibrinogen that has γ-chain residues 390-396 mutated to alanines (Fibγ390-396A). Here, we evaluated binding features using human components, including recombinant fibrinogen variants, FXIII-A2B2, and isolated FXIII-A2and -B2homodimers. FXIII-A2B2coprecipitated with wild-type (γA/γA), alternatively-spliced (γ'/γ'), and αC-truncated (Aα251) fibrinogens, whereas coprecipitation with human Fibγ390-396Awas reduced by 75% (P <0001). Surface plasmon resonance showed γA/γA, γ'/γ', and Aα251 fibrinogens bound FXIII-A2B2with high affinity (nanomolar); however, Fibγ390-396Adid not bind FXIII-A2B2These data indicate fibrinogen residues γ390-396 comprise the major binding motif for FXIII-A2B2Compared with γA/γA clots, FXIII-A2B2activation peptide release was 2.7-fold slower in Fibγ390-396Aclots (P < .02). Conversely, activation of recombinant FXIII-A2(lacking FXIII-B2) was similar in γA/γA and Fibγ390-396Aclots, suggesting fibrinogen residues γ390-396 accelerate FXIII-A2B2activation in a FXIII-B2-dependent mechanism. Recombinant FXIII-B2bound γA/γA, γ'/γ', and Aα251 with similar affinities as FXIII-A2B2, but did not bind or coprecipitate with Fibγ390-396AFXIII-B2also coprecipitated with fibrinogen from FXIII-A-deficient mouse and human plasmas. Collectively, these data indicate that FXIII-A2B2binds fibrinogen residues γ390-396 via the B subunits, and that excess plasma FXIII-B2is not free, but rather circulates bound to fibrinogen. These findings provide insight into assembly of the fibrinogen/FXIII-A2B2complex in both physiologic and therapeutic situations.
authors: Department of Pathology and Laboratory Medicine and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors: James R
authors: JR
authors: Byrnes
authors: Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom; and.
authors: Clare
authors: C
authors: Wilson
authors: Department of Pathology and Laboratory Medicine and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors: Anthony M
authors: AM
authors: Boutelle
authors: Department of Pathology and Laboratory Medicine and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors: Chase B
authors: CB
authors: Brandner
authors: Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH.
authors: Matthew J
authors: MJ
authors: Flick
authors: Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom; and.
authors: Helen
authors: 0000-0002-9199-4201
authors: H
authors: Philippou
authors: Department of Pathology and Laboratory Medicine and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors: Alisa S
authors: 0000-0002-2845-2303
authors: AS
authors: Wolberg
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D004792:Enzyme Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005176:Factor XIII / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005353:Fibronectins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020349:Surface Plasmon Resonance
chemical_list: D004792:Enzyme Precursors; D005353:Fibronectins; D011994:Recombinant Proteins; C064015:factor XIII subunit A; D005176:Factor XIII; C054380:factor XIIIb