Sandbox UVM: Difference between revisions

Factor VIIa (FVIIa) <scene name='Sandbox_UVM/Practice/1'>practice</scene> is a single chain trypsin-like serine protease (EC 3.4.21.21) of 406 residues. The FVII zymogen is a glycoprotein consisting of an amino-terminal (N-linked) γ-carboxyglutamic acid (Gla) domain followed by two epidermal growth factor-like (EGF) domains, a short linker peptide, and a carboxy terminal serine protease domain (Figure 1)1. The Gla domain is responsible for Ca++ binding leading to structural reorganization of FVIIa into a membrane binding protein2. The active form, FVIIa, is generated by a specific cleavage of a peptide bond between Arg-152 and Ile-153 at the end of the linker peptide by either factor Xa (FXa) or thrombin (IIa). This cleavage generates an N-terminal light chain of 152 residues linked to a heavy chain of 254 residues by a disulfide bridge<ref>PMID:10887202</ref><ref>PMID:11953458</ref>. Following cleavage the newly formed N-terminal inserts itself into a cavity, or the activation pocket, forming a salt bridge with Asp343 (Asp194 in trypsin).Formation of this salt bridge allows for the maturation of FVIIa to its active form. FVIIa alone is not very efficient in the insertion of the peptide, however, upon binding to TF the process becomes very efficient.  The insertion of the N-terminus, therefore, facilitates the formation of both the S1 recognition pocket and the oxyanion hole.