Fig. 1

Structural changes predicted to be induced by the R315W mutation. The FVIIa-TF complex (PDB 1DAN) is depicted using UCSF Chimera X [14] as a ribbon structure (panel A, light gray) where the critical residues are labeled (numbering refers to the mature processed form) and shown as ball and stick representations with blue and red for basic and acidic chemical groups, respectively. The structure is oriented such that the R315 region faces out, and the critical features are overlayed with a space-filling representation, where the C170's loop (aa 310–329) shaded in light yellow is adjacent and partially overlapping with the alpha 2 helix (aa 306–313), the protruding R315 region is in light blue, and the activation loop 3 (aa 365–374) [11] is in pink. A similar structural model corresponding to the mutated FVIIa-TF is computationally constructed using the DUET [15], a predictive server that models missense mutations. We replaced the R315 with W to depict the mutation found in our patient (FS) (panel B). The two models are shown in the same orientation (with respect to R315) for easy comparison, and the specific residues and features are maintained as in panel A, except for the W315 and its surrounding region. We utilized the Dunbrack 2010 backbone-dependent rotamer library [16] to estimate the preferred rotamer conformation for our residue of interest. The missense tryptophan 315 was found to prefer an "outward" orientation. The substitution of the R315 with its basic chemical group by a neutral and bulkier W drastically affected the local conformation and electrostatics around the C170's loop due to loss of charge and increased side chain volume. In the bottom part of the figure (panels C and D), the local changes are better visualized using a space-filling model depicting the local surface charges (blue for positive and red for negative) of wild type and mutant FVIIa R315 (panel C) and mutant W315 (panel D). The insets depict the entire VIIa-TF complex for context, with the encircled regions highlighting the regions of interest for the wild type R315 and mutant W315 areas