CPK Color Scheme

Coagulation Factor IX is an important protein in the blood clotting cascade. In humans, Factor IX forms a complex with Factor VIII to activate Factor X. The eventual outcome, after the action of 13 important proteins, is a hard blood clot. Mutations in or absence of Factor IX lead to Hemophilia B.

The buttons below provide an introduction to the structure and function of Factor IX isolated from the venom of a Habu snake.

RESET display to the original wire structure here .

Display Factor IX as its two distinct chains (A appears as dark blue and B appears as light blue) here .

Display tertiary structure of Chain A here .

Display tertiary structure of Chain B here .

Calcium is a cofactor in Coagulation Factor IX, facilitating activation of the concave binding site for Factor VIII. See the calcium ion in its place at the junction of two groups here .

See the concave binding site (between groups A and B) where Factor VIII binds to form a complex that activates Factor X here .



1. Kogoy, John. Chime PDF Manual.

2. Mizuno H. et. al. Crystal structure of coagulation factor IX-binding protein from habu snake venom at 2.6 A: implication of central loop swapping based on deletion in the linker region. Journal of Molecular Biology, May 28, 1999, Vol. 289, 103, 112.

3. Rollason, C. Factor IX. April 8, 2003. < >

4. Wilkinson, Sarah Ann. Coagulation Factor IX. April 8, 2003. < >