title: Purification and characterization of a cloned protease-resistant Treponema pallidum-specific antigen.
abstract: A cloned Treponema pallidum antigen, designated 4D, was purified from Escherichia coli predominantly as a 190-kilodalton (kd) polypeptide, although higher oligomeric forms exist. Extensive proteolysis of 4D created a limit digestion product of 90 kd which retained antigenicity with sera from patients with primary, secondary, early latent, late latent, and tertiary syphilis. A molecule indistinguishable from 90-kd 4D in size, isoelectric point, and antigenicity was isolated from T. pallidum after proteolysis. The 190- and 90-kd forms of 4D were stable at 68 degrees C but converted to 19- and 14-kd species, respectively, after boiling in sodium dodecyl sulfate. The low-molecular-weight species did not react with syphilitic sera. Rabbits immunized with the purified 4D antigen developed antibodies which immobilized virulent T. pallidum in a complement-dependent assay system, suggesting that the antigen has a native surface location.
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D003001:Cloning, Molecular; D003429:Cross Reactions; D006801:Humans; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000378:metabolism; D011817:Rabbits; D013587:Syphilis / Q000276:immunology*; D014210:Treponema pallidum / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D010447:Peptide Hydrolases