title: The riboswitch regulates a thiamine pyrophosphate ABC transporter of the oral spirochete Treponema denticola.
abstract: Thiamine pyrophosphate (TPP), a biologically active form of thiamine (vitamin B₁), is an essential cofactor in all living systems. Microorganisms either synthesize TPP via de novo biosynthesis pathways or uptake exogenous thiamine from the environment via specific transporters. The oral spirochete Treponema denticola is an important pathogen that is associated with human periodontal diseases. It lacks a de novo TPP biosynthesis pathway and needs exogenous TPP for growth, suggesting that it may obtain exogenous TPP via a thiamine transporter. In this study, we identified a gene cluster that encodes a TPP ABC transporter which consists of a TPP-binding protein (TDE0143), a transmembrane permease (TDE0144), and a cytosolic ATPase (TDE0145). Transcriptional and translational analyses showed that the genes encoding these three proteins are cotranscribed and form an operon (tbpABC(Td)) that is initiated by a σ⁷⁰-like promoter. The expression level of this operon is negatively regulated by exogenous TPP and is mediated by a TPP-sensing riboswitch (Td(thi-)(box)). Genetic and biochemical studies revealed that the TDE0143 deletion mutant (T. denticola ΔtbpA) had a decreased ability to transport exogenous TPP, and the mutant failed to grow when exogenous TPP was insufficient. These results taken together indicate that the tbpABC(Td) operon encodes an ABC transporter that is required for the uptake of exogenous TPP and that the expression of this operon is regulated by a TPP-binding riboswitch via a feedback inhibition mechanism.
authors.affiliation: Department of Oral Biology, The State University of New York at Buffalo, Buffalo, New York 14214, USA.
authors.forename: Jiang
authors.initials: J
authors.lastname: Bian
authors.forename: Hongwu
authors.initials: H
authors.lastname: Shen
authors.forename: Youbin
authors.initials: Y
authors.lastname: Tu
authors.forename: Aiming
authors.initials: A
authors.lastname: Yu
authors.forename: Chunhao
authors.initials: C
authors.lastname: Li
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010510:Periodontal Diseases / Q000382:microbiology; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D058928:Riboswitch; D013835:Thiamine Pyrophosphate / Q000378:metabolism*; D048373:Treponema denticola / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014211:Treponemal Infections / Q000382:microbiology
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D012329:RNA, Bacterial; D058928:Riboswitch; D013835:Thiamine Pyrophosphate