Domain organization and crystallographic structure of pro-pseutarin C. (A) Schematics (not to scale) are given depicting the domain organization of P textilis fV and fX. Factor V has a short B domain that can be released by thrombin cleavage at the 2 sites indicated by arrows; however, such processing is unnecessary for cofactor activity. The fX construct used in crystallization studies (EGF2-catalytic domain) is indicated by the bracket. (B) A stereo view of the crystal structure of the fV-fX complex is shown in cartoon representation, with fV colored according to domain (A1 domain in blue, A2 domain in green, A3 domain in yellow, C1 domain in orange, and C2 domain in red) and fX in magenta (EGF2 domain in light pink). The a2 region is shown as green sticks. The orientation shown here is referred to as the front throughout. (C) Close-up of the fV-fX interface.