Figure 3. 3D11 Fab binding to PbCSP repeat peptides.

(A) Affinities of 3D11 Fab for PAPP, NAND, NPND, and Mixed peptides as measured by ITC. Symbols represent independent measurements. Mean K_D values are shown above the corresponding bar. Error bars represent SEM. Peptide sequences are as indicated to the right of the plot, with variable residues underlined and shaded residues indicating those resolved in the corresponding X-ray crystal structures. (B) The 3D11 Fab binds the PAPP (pink), NAND (purple), NPND (blue) and Mixed (red) peptides in nearly identical conformations. mAb 3D11 CDRs are indicated. (C) Overview and side view of the NAND peptide (purple) in the binding groove of the 3D11 Fab shown as surface representation (H-chain shown in black and K-chain shown in gray). (D) Van der Waals interactions formed by side chain atoms of both Ala and Pro residues are indicated by orange dashed lines, and those unique to Pro6 and Pro10 are indicated by green dashed lines.

Figure 3—figure supplement 1. Experimental details of mAb 3D11 binding.

(A) 3D11 Fab binding to peptides representative of the PbCSP αTSR domain (residue 263–318; red) and the full C-terminal domain (residues 202–318; PbC-CSP; blue). PbCSP (residue 24–318) was used as a positive control (black). (B) Composite omit map electron density contoured at 1.0 sigma (blue mesh) around PbCSP peptides PAPP, NAND, NPND and Mixed in complex with the 3D11 Fab. (C) Slight differences in H-bonding at the N- and C-terminal ends of the PbCSP repeat peptides when bound to the 3D11 Fab in the crystal structures. PbCSP peptides are colored as in Figure 3. Antibody residues partaking in H-bonds are colored orange. mAb 3D11 HCDR2 is colored in black and KCDR2 in white.

Figure 3—figure supplement 2. Interactions between mAb 3D11 aromatic side chains and PbCSP peptides.

Interactions formed between PbCSP peptide residues and aromatic side chains of the 3D11 Fab HCDR (black) and KCDR (white). PbCSP peptides are colored as in Figure 3.