Detection and characterization of molecular interfaces of FXIII-Fibrinogen complex by employing integrative hybrid approaches

• Applicant: Dr. Sneha Singh
• Subject Area: Hematology, Oncology ; Structural Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 457324851

The intrinsic and extrinsic pathways of coagulation pathway converge terminally to a common pathway that involves strong role of plasma transglutaminase Factor XIII (FXIII), towards covalent crosslinking of pre-formed fibrin clots, imparting it mechanical strength. A blood-clot is a massive mass of fibrin fibers, precipitating platelets, RBCs, complement, and inflammatory components making it a condensed mass of material that further ensues cessation of bleeding by clump formation and wound healing as a result of activated inflammation. Coagulation Factor XIII is responsible for not just condensing this fibrin mass, but also tethering diverse plasma components onto the clot because of its transglutaminase activity. A conspectus view of these molecules, their roles and behavior in plasma directly indicates that fibrinogen, the precursor of Fibrin acts as a direct effector protein for clot formation whereas FXIII is its direct modifier. In plasma, there exists an interaction of zymogenic FXIII with fibrinogen, however the exact positions, residues, tethering poses, and the effective strength of this interaction is unknown. Given that these zymogens are abundantly present in plasma there have been reports indicating their direct binding to serum albumin which is likely responsible towards its longevity in plasma. In the present proposal, which is an extension of my last DFG grant, I would like to put forward an attempt to characterize the interaction interfaces among FXIII and Fibrinogen in their native zymogenic states as seen in plasma. This will aide in structural assessment of FXIII-Fibrinogen complex. As a part of the proposal, I would also attempt and I am partially successful in resolving the structure of the native Factor XIII- A2B2 complex, which is not available in totality as yet in the protein databases. Understanding the structural interaction behavior of these proteins in plasma would develop insights towards activation modes of both of them that releases active Fibrin and FXIII-A2 for their action, upon injury. This through structural investigation would reveal surface patches in both the molecules that act as interaction interfaces, mapping under-resolved coagulopathies related to FXIII and Fibrinogen will guide us towards understanding them, and hence towards an improved management and care.

• DFG Programme: Research Grants
• Co-Investigator: Privatdozent Arijit Biswas, Ph.D.