Characterization of biologically active domains on elastin: identification of a monoclonal antibody to a cell recognition site.

Monoclonal antibodies to bovine alpha-elastin were characterized with solid-phase ELISA, Western blot, immunoprecipitation, and immunoaffinity chromatography. One monoclonal antibody, BA-4, bound to insoluble elastin, alpha-elastin, and tropoelastin and to peptide fragments generated by proteolytic digestion of insoluble elastin. Immunoaffinity chromatography of elastin fragments released from insoluble elastin with pancreatic elastase demonstrated that BA-4 was specific for a chemotactically active epitope composed of valine, glycine, alanine, and proline in a molar ratio of approximately 2:2:1:1. This composition matches the Val-Gly-Val-Ala-Pro-Gly repeating sequence in elastin that has been shown to be a chemoattractant for fibroblasts and monocytes. Specific ablation of the chemotactic activity of synthetic Val-Gly-Val-Ala-Pro-Gly by BA-4 IgG confirmed the identity of the epitope recognized by the monoclonal antibody and suggests that, despite its hydrophobic nature, this cell recognition domain is accessible on the surface of elastin and is strongly immunogenic. BA-4 should prove useful for investigating cell surface receptors for elastin.