title: Properties of an ordered ring structure formed by recombinant Treponema pallidum surface antigen 4D.
abstract: Ultrastructural and biochemical studies of a recombinant Treponema pallidum surface antigen designated 4D have been conducted due to its likely biological significance. Electron microscopy demonstrated that the 190-kilodalton (kDa) 4D molecule is an ordered ring structure of 10-nm diameter. The 90-kDa proteinase K-treated 4D is an ordered ring structure of 6-nm diameter. Evidence is presented that the 190-kDa ordered ring is maintained by noncovalent bonds; 19-kDa monomers can reassociate in vitro to reform a 190-kDa molecule. Amino acid composition analysis of 190-kDa 4D showed that the molecule is composed of 45% hydrophobic residues. Evidence relating the structure of the 4D ordered ring to its potential role in the pathogenesis of syphilis is discussed.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000942:Antigens, Bacterial / Q000032:analysis / Q000302:isolation & purification; D000954:Antigens, Surface / Q000032:analysis / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000032:analysis / Q000276:immunology; D055598:Chemical Phenomena; D002621:Chemistry; D003001:Cloning, Molecular; D019286:Endopeptidase K; D010450:Endopeptidases / Q000494:pharmacology; D008854:Microscopy, Electron; D008970:Molecular Weight; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000032:analysis / Q000276:immunology*; D014210:Treponema pallidum / Q000276:immunology*
chemical_list: D000596:Amino Acids; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D011994:Recombinant Proteins; D010450:Endopeptidases; D019286:Endopeptidase K