title: Identification and transcriptional analysis of a Treponema pallidum operon encoding a putative ABC transport system, an iron-activated repressor protein homolog, and a glycolytic pathway enzyme homolog.
abstract: We have characterized a 5.2-kilobase (kb) putative transport related operon (tro) locus of Treponema pallidum subsp. pallidum (Nichols strain) (Tp) encoding six proteins: TroA, TroB, TroC, TroD, TroR and Phosphoglycerate mutase (Pgm). Four of these gene products (TroA-TroD) are homologous to members of the ATP-Binding Cassette (ABC) superfamily of bacterial transport proteins. TroA (previously identified as Tromp1) has significant sequence similarity to a family of Gram-negative periplasmic substrate-binding proteins and to a family of streptococcal proteins that may have dual roles as substrate binding proteins and adhesins. TroB is homologous to the ATP-binding protein component, whereas TroC and TroD are related to the hydrophobic membrane protein components of ABC transport systems. TroR is similar to Gram-positive iron-activated repressor proteins (DesR, DtxR, IdeR, and SirR). The last open reading frame (ORF) of the tro operon encodes a protein that is highly homologous to the glycolytic pathway enzyme, Pgm. Primer extension results demonstrated that the tro operon is transcribed from a sigma 70-type promoter element. Northern analysis and reverse transcriptase-polymerase chain reactions provided evidence for the presence of a primary 1-kb troA transcript and a secondary, less abundant, troA-pgm transcript. The tro operon is flanked by a Holliday structure DNA helicase homolog (upstream) and two ORFs representing a purine nucleoside phosphorylase homolog and tpp15, a previously characterized gene encoding a membrane lipoprotein (downstream). The presence of a complex operon containing a putative ABC transport system and a DtxR homolog indicates a possible linkage between transport and gene regulation in Tp.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Texas, Houston Medical School 77225-0708, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Hardham
authors.forename: L V
authors.initials: LV
authors.lastname: Stamm
authors.forename: S F
authors.initials: SF
authors.lastname: Porcella
authors.forename: J G
authors.initials: JG
authors.lastname: Frye
authors.forename: N Y
authors.initials: NY
authors.lastname: Barnes
authors.forename: J K
authors.initials: JK
authors.lastname: Howell
authors.forename: S L
authors.initials: SL
authors.lastname: Mueller
authors.forename: J D
authors.initials: JD
authors.lastname: Radolf
authors.forename: G M
authors.initials: GM
authors.lastname: Weinstock
authors.forename: S J
authors.initials: SJ
authors.lastname: Norris
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D005798:Genes, Bacterial / Q000235:genetics; D007501:Iron / Q000494:pharmacology; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D009876:Operon / Q000235:genetics*; D033902:Periplasmic Binding Proteins; D010736:Phosphoglycerate Mutase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D012097:Repressor Proteins / Q000235:genetics*; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014210:Treponema pallidum / Q000235:genetics*
chemical_list: D018528:ATP-Binding Cassette Transporters; D033902:Periplasmic Binding Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012097:Repressor Proteins; C120377:TroA protein, Treponema pallidum; D007501:Iron; D010736:Phosphoglycerate Mutase