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Identification and sequences of the Treponema pallidum mglA and mglC genes
L V Stamm1, N R Young, J G Frye
1Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill 27599-7400, USA. Istamm@email.unc.edu
Abstract:
Treponema pallidum, the agent of syphilis, cannot be continuously cultivated in vitro. To identify treponemal genes encoding exported proteins, we performed TnphoA mutagenesis of a T. pallidum genomic DNA library in Escherichia coli. Clone 6D2 was chosen for further study based on partial nucleotide sequence obtained from p6D2 containing a TnphoA insertion. A complete open reading frame (orf1) and a truncated orf (orf2) were identified in the treponemal DNA of p6D2. Orf1 encodes a hydrophobic protein of 531 amino acids with a calculated M(r) of 57,882 Da. The deduced amino acid sequence of Orf1 has homology to the MglC proteins of E. coli, Haemophilus influenzae, and Salmonella typhimurium. T. pallidum Orf1 (MglC) contains a conserved motif that is found in integral cytoplasmic membrane proteins of ATP-binding cassette (ABC) transport systems. T. pallidum orf2 encodes a protein of 496 amino acids with a calculated M(r) of 55,547 Da. The deduced amino acid sequence of Orf2 has homology to the MglA proteins of S. typhimurium, E. coli, H. influenzae, and Mycoplasma genitalium. Orf2 (MglA) contains two consensus ATP-binding motifs. T. pallidum mglA and mglC are located downstream of mglB, consistent with the gene order of previously identified mgl operons. The putative T. pallidum mgl operon encodes the first high-affinity ABC transport system identified in this spirochete.
Insights
Researchers identified a novel high-affinity ATP-binding cassette (ABC) transport system in Treponema pallidum, the bacterium causing syphilis. This discovery offers new insights into treponemal biology and potential therapeutic targets.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Treponema pallidum, the causative agent of syphilis, presents significant challenges for in vitro cultivation.
- Identifying genes encoding exported proteins is crucial for understanding T. pallidum pathogenesis.
Purpose of the Study:
- To identify genes responsible for exported proteins in Treponema pallidum.
- To characterize a novel ATP-binding cassette (ABC) transport system in T. pallidum.
Main Methods:
- Utilized TnphoA mutagenesis of a T. pallidum genomic DNA library in Escherichia coli.
- Sequenced and analyzed DNA from a selected clone (6D2) containing a TnphoA insertion.
- Deduced protein sequences and identified homologies to known proteins and conserved motifs.
Main Results:
- Identified two open reading frames (orf1 and orf2) in T. pallidum DNA.
- Orf1 encodes a protein (MglC) with homology to MglC proteins and containing an ABC transport system motif.
- Orf2 encodes a protein (MglA) with homology to MglA proteins and containing ATP-binding motifs.
- The mglA and mglC genes are located downstream of mglB, suggesting an mgl operon structure.
- This represents the first identified high-affinity ABC transport system in T. pallidum.
Conclusions:
- The putative T. pallidum mgl operon encodes a functional high-affinity ABC transport system.
- This system is likely involved in nutrient uptake or other essential cellular processes in T. pallidum.
- The identified ABC transporter represents a potential target for novel anti-syphilis therapies.