IDENTIFICATION AND PURIFICATION OF NOVEL INTERNALIN-RELATED PROTEINS IN LISTERIA-MONOCYTOGENES AND LISTERIA-IVANOVII

Monoclonal antibodies were generated against a 30-kDa protein fraction derived from culture supernatants of a Listeria monocytogenes strain complemented with additional copies of the prfA regulator gene, Severa l of the antibodies reacted specifically with a hitherto unidentified, secreted 30-kDa polypeptide, By immunoblot analysis, the expression o f this 30-kDa polypeptide was found to be dependent on the presence of the PrfA regulator protein, Microsequencing of peptides derived from the partially purified 30 kBa protein revealed homologies to the InlA and InlB polypeptides of L. monocytogenes, which are required for the internalization. of the bacteria into nonphagocytic cell lines, This p rompted us to term the 30-kDa polypeptide internalin-related protein ( Irp). Irp-specific monoclonal antibodies cross-reacted with a 24-kDa p olypeptide present in culture supernatants of Listeria ivanovii, indic ating the existence of an Irp-related protein In this pathogenic Liste ria species.