Surface of interaction between FVa and APC. Both FVa (A) and APC (B) are shown facing the reader (small insets) to expose the surface of interaction (zoom sections) and its constituent residues (green sticks surrounded by yellow density) involved in contacts within 4.0 Å (Figure 5; Table 2). (A) Residues of FVa involved in APC binding include the region around the site of cleavage at R506 (Figure 6A) and residues within the 310 and 380 segments. In the latch, only residues D660 and E669 make direct interactions with APC. (B) Residues of APC involved in FVa binding include the autolysis loop (300 segment), the 30-loop (190 segment), the 60-loop (210 segment), the 70-loop (230 segment), and the active site housing D354(c189) in the S1 site.