Identification of the peptidic sequence recognized by BV6.

(A) Peptide scan of VE-cadherin extracellular region. Peptides of 15 AA spanning the entire extracellular domain of the protein were synthesized and tested for mAb recognition (arrows indicate the peptide spots recognized).41 mAb Cad 5 bound to peptide 31: KVFRVDAETGDVFAI; mAb BV6 bound to peptides 112 to 115 containing the sequence TIDLRY. (B) The peptides containing TIDLRY corresponding to VE-cadherin sequences AA 334 to 357 and AA 340 to 354 and the scrambled peptide (APRTDIAEINDGYPVTSMRFPALS) were tested in competition ELISA experiments. (Bi) The binding of soluble BV6 and BV9 (0.5 μg/mL) to purified VE-cadherin recombinant fragment (VE1-Ig, 1 μg/mL) coated on plastic was tested in the presence or absence of the peptides (200 μM). TIDLRY peptides blocked BV6 but not BV9 binding. (Bii) Flow cytometric analysis of BV6 binding to endothelial cells expressing VE-cadherin. Peptides containing TIDLRY sequence but not scrambled peptides blocked the binding of BV6.