Clinical Research Center, University of Debrecen, Medical and Health Science Center, Debrecen, Hungary; and.
Blood. 2014 Mar 13;123(11):1757-63. doi: 10.1182/blood-2013-10-533596. Epub 2014 Jan 9.
Coagulation factor XIII (FXIII) is a heterotetramer consisting of 2 catalytic A subunits (FXIII-A2) and 2 protective/inhibitory B subunits (FXIII-B2). FXIII-B, a mosaic protein consisting of 10 sushi domains, significantly prolongs the lifespan of catalytic subunits in the circulation and prevents their slow progressive activation in plasmatic conditions. In this study, the biochemistry of the interaction between the 2 FXIII subunits was investigated. Using a surface plasmon resonance technique and an enzyme-linked immunosorbent assay-type binding assay, the equilibrium dissociation constant (Kd) for the interaction was established in the range of 10(-10) M. Based on the measured Kd, it was calculated that in plasma approximately 1% of FXIII-A2 should be in free form. This value was confirmed experimentally by measuring FXIII-A2 in plasma samples immunodepleted of FXIII-A2B2. Free plasma FXIII-A2 is functionally active, and when activated by thrombin and Ca(2+), it can cross-link fibrin. In cerebrospinal fluid and tears with much lower FXIII subunit concentrations, >80% of FXIII-A2 existed in free form. A monoclonal anti-FXIII-B antibody that prevented the interaction between the 2 subunits reacted with the recombinant combined first and second sushi domains of FXIII-B, and its epitope was localized to the peptide spanning positions 96 to 103 in the second sushi domain.
凝血因子 XIII (FXIII) 是一种由 2 个催化 A 亚基 (FXIII-A2) 和 2 个保护/抑制 B 亚基 (FXIII-B2) 组成的杂四聚体。FXIII-B 是一种由 10 个 sushi 结构域组成的镶嵌蛋白，可显著延长催化亚基在循环中的寿命，并防止其在血浆条件下缓慢渐进激活。在这项研究中，研究了 2 个 FXIII 亚基之间相互作用的生物化学。使用表面等离子体共振技术和酶联免疫吸附测定型结合测定法，确定了相互作用的平衡解离常数 (Kd) 在 10(-10) M 的范围内。根据测量的 Kd 值计算得出，在血浆中约有 1%的 FXIII-A2 应该处于游离状态。通过测量免疫耗尽 FXIII-A2B2 的血浆样品中的 FXIII-A2 ，证实了该值在实验中。游离的血浆 FXIII-A2 具有功能活性，当被凝血酶和 Ca(2+) 激活时，它可以交联纤维蛋白。在脑脊液和眼泪中，FXIII 亚基浓度低得多，>80%的 FXIII-A2 以游离形式存在。一种阻止 2 个亚基相互作用的单克隆抗 FXIII-B 抗体与 FXIII-B 的重组第一和第二 sushi 结构域结合，并将其表位定位于第二 sushi 结构域的 96 至 103 位氨基酸肽段。
