[Identification of the epitope of von Willebrand factor recognized by monoclonal antibody SZ-125 with immune-affinity mass spectrometry].

Objective: To identify the epitope of von Willebrand factor (vWF) recognized by monoclonal antibody SZ-125 (mAb SZ-125) using immune-affinity matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) assay in combination with peptide synthesis and amino acid site-mutagenesis technology.
Methods: Recombinant vWF A3 domain (rVWF A3) was directly affinity bound to SZ-125 antibody beads and proselytized by trypsin. The digested peptide fragments were then measured using MALDI-TOF-MS. The detected peptide sequence by MALDI-TOF-MS was synthesized and several amino-acids in it were mutated to test its affinity with mAb SZ-125.
Results: The epitope of rVWF A3 recognized by SZ-125 was identified to be the peptide fragment(1001);EGGPSQIGDALGFAVR(1016);. Synthesized peptide NH2;-EGGPSQIGDALGFAVR-COOH could bind to mAb SZ125.
Results: of site-directed mutagenesis revealed that amino acids E1001, F1013, V1015 and R1016 played critical roles in the binding between mAb SZ-125 and rVWF A3.
Conclusion: The epitope of rVWF A3 recognized by mAb SZ-125 has been accurately confirmed using immune-affinity mass spectrometry in combination with peptide synthesis and site-directed mutagenesis of special amino acids.