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A mgl-like operon in Treponema pallidum, the syphilis spirochete
S F Porcella1, T G Popova, K E Hagman
1Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Abstract:
A 38-kDa lipoprotein of Treponema pallidum subsp. pallidum (T. pallidum), the syphilis spirochete, previously was identified as a putative homolog of E. coli MglB [Becker et al. (1994) Infect. Immun. 62, 1381-1391]. In the present study, genome walking in regions adjacent to the T. pallidum 38-kDa lipoprotein gene has identified three contiguous genes (tp-mglB [formerly tpp38], tp-mglA, and tp-mglC) which appear to comprise a mgl-like operon in T. pallidum. A prominent transcript corresponding to tp-mglB, the first gene of the operon which encodes the carbohydrate receptor, is synthesized by T. pallidum along with lesser abundant transcript(s) corresponding to the entire T. pallidum mgl operon. An active promoter 135 bp upstream of tp-mglB is believed to direct mRNA synthesis for the operon. This is the first membrane protein-encoding operon of T. pallidum for which a putative function (glucose import) has been assigned. Furthermore, by analogy with E. coli MglB which interacts with the sensory transducer Trg to induce a chemotactic response, it is possible that T. pallidum also contains a homolog of E. coli Trg or other methyl-accepting chemotaxis proteins. The existence of a mgl operon in T. pallidum thus may have important implications with respect to T. pallidum survival, tissue dissemination, and sensory transduction during virulence expression.
Insights
Researchers discovered a new gene operon in Treponema pallidum, the syphilis bacterium. This operon, similar to E. coli
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Treponema pallidum subsp. pallidum (T. pallidum) is the causative agent of syphilis.
- A previously identified 38-kDa lipoprotein was a putative homolog of E. coli MglB.
Purpose of the Study:
- To identify and characterize genes associated with the T. pallidum 38-kDa lipoprotein.
- To investigate the potential function and implications of a newly discovered gene cluster in T. pallidum.
Main Methods:
- Genome walking was employed to identify genes adjacent to the T. pallidum 38-kDa lipoprotein gene.
- Transcriptional analysis was performed to study gene expression within the identified operon.
- Bioinformatic analysis and comparison with E. coli homologs were used to infer function.
Main Results:
- Three contiguous genes, tp-mglB, tp-mglA, and tp-mglC, forming a mgl-like operon in T. pallidum, were identified.
- A prominent transcript for tp-mglB (carbohydrate receptor) and less abundant transcripts for the entire operon were detected.
- The operon is likely regulated by a promoter upstream of tp-mglB, suggesting a role in glucose import.
- This represents the first functional assignment for a membrane protein-encoding operon in T. pallidum.
Conclusions:
- The T. pallidum mgl operon is likely involved in glucose import.
- The presence of this operon suggests potential roles in T. pallidum survival, dissemination, and sensory transduction.
- Homologs of E. coli Trg or other methyl-accepting chemotaxis proteins may exist in T. pallidum, impacting virulence.