Tissue factor activates allosteric networks in factor VIIa through structural and dynamic changes.
BACKGROUND
Tissue factor (TF) promotes colocalization of enzyme (factor VIIa) and substrate (FX or FIX), and stabilizes the active conformation of FVIIa. Details on how TF induces structural and dynamic changes in the catalytic domain of FVIIa to enhance its efficiency remain elusive.


OBJECTIVE
To elucidate the activation of allosteric networks in the catalytic domain of the FVIIa protease it is when bound to TF.


METHODS
Long-timescale molecular dynamics simulations of FVIIa, free and in complex with TF, were executed and analyzed by dynamic network analysis.


RESULTS
Allosteric paths of correlated motion from the TF contact point, Met306, in FVIIa to the active site triad can be described and quantified. In particular, the shortest paths from Met306 to Ser344 and His193 are 16% and 8% longer in free FVIIa than in TF-FVIIa, and they encompass previously undiscovered residue-residue interactions that are not likely to be inferred from mutagenesis studies. Furthermore, paths from Met306 to Ile153 (N-terminus) and Trp364, both representing hallmark residues of allostery, are 7% and 37% longer, respectively, in free FVIIa. Thus, there is significantly weaker coupling between the TF contact point and key residues in the catalytic domain of FVIIa, causing the active site triad to disintegrate in the simulation when TF is not present.


CONCLUSIONS
These findings complement our current understanding of how the protease FVIIa is stimulated by TF. We demonstrate allosteric networks in the catalytic domain that are activated by TF and help to make FVIIa an efficient catalyst of FIX and FX activation.
Haemophilia Biochemistry, Novo Nordisk A/S, Måløv, Denmark; DTU Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark.
J J
JJ
Madsen
E
E
Persson
O H
OH
Olsen
D000494:Allosteric Regulation; D001665:Binding Sites; D020134:Catalytic Domain; D004789:Enzyme Activation; D015942:Factor VIIa / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013925:Thromboplastin / Q000737:chemistry / Q000378:metabolism*
D013925:Thromboplastin; D015942:Factor VIIa
allosteric regulation; allosteric site; coagulation factor VIIa; molecular dynamics simulations; tissue factor