Crystal structures of (NPNA)3 peptides in complex with Fab311 and Fab317. (A and B) Surface representation of the variable domains of Fab311 (A) and Fab317 (B) with the (NPNA)3 peptide represented by a red tube. The heavy- and light-chain variable domains are colored dark and light gray, respectively. (C and D) Paratope representation for Fab311 (C) and Fab317 (D) with a transparent dark gray surface for the heavy chain and a transparent light gray surface for the light chain. The underlying CDR loops are shown in cartoon representation and are colored green (H1), blue (H2), red (H3), light green (L1), light blue (L2), and pink (L3). The (NPNA)3 peptide is shown in stick representation (yellow carbons). The N terminus of each peptide is indicated (Nterm).