title: Cellular and extracellular protein antigens of Treponema pallidum synthesized during in vitro incubation of freshly extracted organisms.
abstract: A new medium that permits radiolabeling of freshly extracted cells of Treponema pallidum with [35S]methionine very efficiently has been devised. Although treponemes were not purified free of contaminating rabbit tissue, label was incorporated exclusively into treponemal protein in a linear manner for at least the first 16 h of in vitro incubation. Throughout this period, virtually a full complement of treponemal proteins was synthesized, based on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis comparison of the radiolabeled protein profile with the Coomassie blue-stained profile of gradient-purified treponemes. The radiolabeled protein profiles obtained with three pathogenic strains were very similar but not identical. Using solubilized treponemal extracts and a sensitive radioimmunoprecipitation procedure, we identified the protein antigens of T. pallidum that were recognized by immunoglobulin G antibodies in various rabbit and human syphilitic sera. A simple fractionation procedure has been used to separate soluble and membrane-bound treponemal proteins. A number of the membrane proteins are exposed on the cell surface, since intact radiolabeled treponemes bound antibodies directed against these proteins. In addition, a unique class of low-molecular-weight extracellular treponemal proteins has been identified. The cell surface-exposed proteins were among the earliest proteins recognized by immunoglobulin G antibodies after experimental infection of rabbits with T. pallidum.
mesh_terms: D000828:Animal Population Groups; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000276:immunology*; D005110:Extracellular Space / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008565:Membrane Proteins / Q000276:immunology; D008715:Methionine; D008970:Molecular Weight; D011817:Rabbits; D012995:Solubility; D013045:Species Specificity; D013587:Syphilis / Q000276:immunology; D014210:Treponema pallidum / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D007074:Immunoglobulin G; D008565:Membrane Proteins; D008715:Methionine