<p>(A) Sequence alignment of the CAP248-2B heavy and light chain with their predicted V- and J-gene precursors. The CDRs are shaded, labelled, and colored. The heavy chain FR3 is similarly indicated in blue. (B) Crystal structure of the CAP248-2B Fab. The light and heavy chains are colored olive and forest green respectively, while CDR loops and FR-H3 are colored according to A. Two views are shown around a ~45° axis to highlight the long CDR-L3 (yellow). Insets show the conformational differences between the CDR-H3 and CDR-L3 loops between Fab structure 1 (shown here) and Fab structure 2 (shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006074#ppat.1006074.s001" target="_blank">S1 Fig</a>). Two Fabs were present in both asymmetric units, so four loops are shown per inset, two for Fab1 CDR-H3 (red) or L3 (yellow), and two for Fab2 CDR-H3 and L3 (both grey). Asp<sup>100B</sup> and Asp<sup>100C</sup> in the heavy chain and Phe<sup>95C</sup> and Phe<sup>95D</sup> in the light chain are shown with stick representations to highlight the conformational divergence between the two structures. Due to crystal packing all downstream analyses were based on the 3.1 Å Fab1 structure.</p
