Initiates blood coagulation by forming a complex with circulating factor VII or VIIa. The [TF:VIIa] complex activates factors IX or X by specific limited proteolysis. TF plays a role in normal hemostasis by initiating the cell-surface assembly and propagation of the coagulation protease cascade. Interacts with HSPE; the interaction, inhibited by heparin, promotes the generation of activated factor X and activates coagulation in the presence of activated factor VII. Brain, heart. Belongs to the tissue factor family.