Factor IX: Difference between revisions

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<scene name='Factor_IX/Ixstructure_egf1/1'>EGF-1</scene> and <scene name='Factor_IX/Ixstructure_egf2/1'>EGF-2</scene>). The N-terminus of <scene name='Factor_IX/Ixstructure_egf1/1'>EGF-1</scene> contains a Ca2+ binding site, while the C-terminus connects to a hydrophobic pocket of <scene name='Factor_IX/Ixstructure_egf2/1'>EGF-2</scene> and a salt bridge through Lys122 (<scene name='Factor_IX/Ixstructure_egf1/1'>EGF-1</scene> residue) and Gln74 (<scene name='Factor_IX/Ixstructure_egf2/1'>EGF-2</scene>). <scene name='Factor_IX/Ixstructure_egf2/1'>EGF-2</scene> connects to the <scene name='Factor_IX/Ixstructure_chainc/1'>serine protease</scene> domain through a linker peptide and is required for a proper orientation and folding of <scene name='Factor_IX/Ixstructure_chainc/1'>serine proteases</scene>. To have a physiologically active factor IX, two cleaves must occur to remove a 35 amino acid region that precedes the catalytic region. The first cleave is at Arg145, generating an inactive FIXα. The second cleavage is at Arg180 results in a catalytically active molecule FIXaβ. This resulting heterodimer is held by a disulfide bridge at Cys132-Cys289. The <scene name='Factor_IX/Ixstructure_chainc/1'>serine protease</scene>  contains a catalytic triad of <scene name='Factor_IX/Ixstructure_catalytictriad/1'>His221, Asp269, and Ser365</scene>. Upon cleave at Arg180, Val181 can form a salt bridge with Asp364, which is a characteristic of active <scene name='Factor_IX/Ixstructure_chainc/1'>serine proteases</scene>. The active FIXa, can then interact with its cofactor, FVIIIa, to form a membrane-bound Xase complex, which activated FX to FXa.