Figure 3

Details of epitope interactions of C5.2. (a) A stereo view of key residues involved in antigen binding with their side chains shown as sticks. Note (i) the main-chain hydrogen bonds Thr^L92 to Tyr³⁹⁴ and Leu^L94 to Ile³⁹², (ii) CDR-H3 pSer³⁹⁶ phospho-specific contacts from Arg^H32, Arg^H95, Gly^H96, and Thr^H97 with coordinating water molecules (yellow balls), (iii) intermolecular hydrogen bond between Tyr³⁹⁴ and pSer³⁹⁶, and (iv) additional contacts from His^L91 and Thr^H33. Hydrogen bonds are represented by dashed black lines and labeled with bond distance. (b) Key residues from CDR-H1 involved in the orphan phosphate recognition. Note (i) hydrogen bond with Thr^H28, (ii) salt bridge with Arg^H32, and (iii) noncovalent contacts with Tyr^H27 and Asp^H31. (c) A schematic of C5.2 antibody-antigen interactions. Hydrogen bonds are represented by dashed black lines and van der Waals forces denoted by eyelashes. Residues in cyan ovals are from light chain and those in light green ovals from heavy chain. Residues in solid ovals contribute to the interaction by their main chain atoms, and those in dashed ovals contribute to the interaction by their side chain atoms.