STRUCTURAL REQUIREMENTS FOR BINDING OF BRADYKININ TO ANTIBODY .3. EFFECT OF CARRIER ON ANTIBODY SPECIFICITY

Binding of bradykinin, alanine analogs of bradykinin, and fragments of bradykinin has been examined in a radioimmunoassay employing the intrinsically labeled peptide.The antibodies used were elicited by immunization with bradykinin coupled to poly-L-lysine, bradykinin coupled to ovalbumin, or human kininogen I. A single antiserum directed against bradykinin-polylysine appeared to be functionally homogeneous and to recognize bradykinin in a preferred conformation which required its entire nonapeptide sequence. This was indicated by the importance of the prolines in positions 2 and 3 and the glycine in position 4 and by the inability of fragments incorporating this region to bind to antibody. Two antisera against bradykinin- ovalbumin were functionally heterogeneous. They required for binding the aromatic residues in positions 5 and 8 as they exist in the proper nonapeptide sequence. An antiserum against human kininogen I was also heterogeneous and was directed primarily against the carboxyl-terminal residues of bradykinin. These results indicate that antibodies of varying specificities may be directed against a short defined amino acid sequence. The nature of the carrier of the immunogen ma play a significant role in determining the homogeneity and specificity of antibody directed against bradykinin. © 1969, American Chemical Society. All rights reserved.