Purification of the 230-kD bullous pemphigoid antigen (BP230) from bovine tongue mucosa: structural analyses and assessment of BP230 tissue distribution using a new monoclonal antibody.

In the epidermis the autoantigen BP230 is a component of the hemidesmosomal plaque. We have developed a procedure for the isolation of BP230 from bovine tongue mucosa using chromatographic means. The identity of the isolated protein was confirmed by its recognition by bullous pemphigoid autoantibodies. A monoclonal antibody (MoAb230), generated against the purified protein, localizes to the region of the plaque of the hemidesmosome with which keratin bundles interact. Furthermore, the tissue distribution of BP230, assessed using MoAb230, suggests that BP230 or an immunologically related protein is a component of all hemidesmosomes. Ultrastructural analyses of the BP230 preparation reveal that the BP230 molecules assemble into macromolecular aggregates. The few images of individual intact molecules that we have observed in platinum replicas of rotary shadowed BP230 preparations suggest that BP230 is an elongate rod-shaped molecule. This is consistent with predictions based on the primary sequence of BP230 deduced from BP230 cDNAs reported by others. We discuss our results in relation to the potential function of BP230. Isolation of BP230 should now allow more rigorous biochemical analyses of potential protein-protein interactions of BP230 in the hemidesmosome.