Fine Specificity of Ligand-Binding Domain 1 in the Polymeric Ig Receptor: Importance of the CDR2-Containing Region for IgM Interaction

摘要: The human polymeric Ig receptor (pIgR), also called transmembrane secretory component, is expressed basolaterally on exocrine epithelia, and mediates specific external transport of dimeric IgA pentameric IgM. extracellular part pIgR consists five Ig-like domains (D1-D5), a highly conserved D1 region appears to mediate the initial noncovalent ligand interaction. While binds both IgM with high affinity, rabbit counterpart has virtually no binding capacity for This remarkable disparity constitutes evidence that site two ligands differs regard essential contact elements. Therefore, we human/rabbit chimeric pIgRs in Madin-Darby canine kidney cells found crucial interaction when placed context full-length regardless its backbone species. contains three complementarity-determining region-like loops (CDR1–3), further map regions involved binding, transfected receptors which containing CDR-like had been interchanged. Our results showed CDR2-like loop most binding. CDR1-like contributed substantially this interaction, whereas only little contribution was provided by CDR3-like loop, although it appeared be necessary maximal