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Liu Z, Zhang X, Xiong S, Huang S, Ding X, Xu M, Yao J, Liu S, Zhao F. Endothelial dysfunction of syphilis: Pathogenesis. J Eur Acad Dermatol Venereol 2024. [PMID: 38376088 DOI: 10.1111/jdv.19899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 01/19/2024] [Indexed: 02/21/2024]
Abstract
Treponema pallidum is the causative factor of syphilis, a sexually transmitted disease (STD) characterized by perivascular infiltration of inflammatory cells, vascular leakage, swelling and proliferation of endothelial cells (ECs). The endothelium lining blood and lymphatic vessels is a key barrier separating body fluids from host tissues and is a major target of T. pallidum. In this review, we focus on how T. pallidum establish intimate interactions with ECs, triggering endothelial dysfunction such as endothelial inflammation, abnormal repairment and damage of ECs. In addition, we summarize that migration and invasion of T. pallidum across vascular ECs may occur through two pathways. These two mechanisms of transendothelial migration are paracellular and cholesterol-dependent, respectively. Herein, clarifying the relationship between T. pallidum and endothelial dysfunction is of great significance to provide novel strategies for diagnosis and prevention of syphilis, and has a great potential prospect of clinical application.
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Affiliation(s)
- Zhaoping Liu
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Xiaohong Zhang
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Shun Xiong
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Shaobin Huang
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Xuan Ding
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Man Xu
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Jiangchen Yao
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Shuangquan Liu
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
| | - Feijun Zhao
- Institute of Pathogenic Biology and Key Laboratory of Special Pathogen Prevention and Control of Hunan Province, Hengyang Medical College, University of South China, Hengyang, China
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang, China
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Li S, Li W, Jin Y, Wu B, Wu Y. Advancements in the development of nucleic acid vaccines for syphilis prevention and control. Hum Vaccin Immunother 2023; 19:2234790. [PMID: 37538024 PMCID: PMC10405752 DOI: 10.1080/21645515.2023.2234790] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 06/12/2023] [Accepted: 07/05/2023] [Indexed: 08/05/2023] Open
Abstract
Syphilis, a chronic systemic sexually transmitted disease, is caused by the bacterium Treponema pallidum (T. pallidum). Currently, syphilis remains a widespread infectious disease with significant disease burden in many countries. Despite the absence of identified penicillin-resistant strains, challenges in syphilis treatment persist due to penicillin allergies, supply issues, and the emergence of macrolide-resistant strains. Vaccines represent the most cost-effective strategy to prevent and control the syphilis epidemic. In light of the ongoing global coronavirus disease 2019 (COVID-19) pandemic, nucleic acid vaccines have gained prominence in the field of vaccine research and development, owing to their superior efficiency compared to traditional vaccines. This review summarizes the current state of the syphilis epidemic and the preliminary findings in T. pallidum nucleic acid vaccine research, discusses the challenges associated with the development of T. pallidum nucleic acid vaccines, and proposes strategies and measures for future T. pallidum vaccine development.
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Affiliation(s)
- Sijia Li
- Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, Institution of Pathogenic Biology, University of South China, Hengyang, China
| | - Weiwei Li
- Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, Institution of Pathogenic Biology, University of South China, Hengyang, China
- Department of Clinical Laboratory, The Second People’s Hospital of Foshan, Foshan, China
| | - Yinqi Jin
- Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, Institution of Pathogenic Biology, University of South China, Hengyang, China
| | - Bin Wu
- First Affiliated Hospital, Guangdong Medical University, Zhanjiang, Guangdong, China
| | - Yimou Wu
- Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, Institution of Pathogenic Biology, University of South China, Hengyang, China
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Tanno-Nakanishi M, Kikuchi Y, Kokubu E, Yamada S, Ishihara K. Treponema denticola transcriptional profiles in serum-restricted conditions. FEMS Microbiol Lett 2019; 365:5049473. [PMID: 29982599 DOI: 10.1093/femsle/fny171] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 07/04/2018] [Indexed: 12/13/2022] Open
Abstract
Treponema denticola is a major pathogen in periodontal disease and is frequently isolated from the lesions of patients with chronic periodontitis. Treponema denticola utilizes serum components as nutrient sources so as to colonize and proliferate in the gingival crevice. However, the mechanisms of serum utilization remain unclear. Therefore, the aim of the present study was to identify T. denticola serum utilization genes. Precultured T. denticola cells were suspended in a tryptone-yeast extract-gelatin-volatile fatty acids medium containing 0, 1% and 10% serum, respectively, and incubated anaerobically for 17 h. Total RNA was isolated, and T. denticola gene expression was compared by microarray and reverse transcription-polymerase chain reaction. In serum-depleted conditions, the expression levels of a potential hydroxylamine reductase, several ABC transporters, and phosphoenolpyruvate synthase were increased, while those of genes encoding methyl-accepting chemotaxis proteins and a transcriptional regulator were decreased. These results suggest that T. denticola may uptake serum components mainly through the action of ABC transporters. In particular, the decrease in the dmcA expression level with decreasing serum concentration suggests its involvement in chemotaxis toward serum-rich environments.
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Affiliation(s)
- Mariko Tanno-Nakanishi
- Department of Periodontology, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Yuichiro Kikuchi
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan.,Oral Health Science Center, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Eitoyo Kokubu
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan.,Oral Health Science Center, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Satoru Yamada
- Department of Periodontology, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Kazuyuki Ishihara
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan.,Oral Health Science Center, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
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Mikalová L, Strouhal M, Oppelt J, Grange PA, Janier M, Benhaddou N, Dupin N, Šmajs D. Human Treponema pallidum 11q/j isolate belongs to subsp. endemicum but contains two loci with a sequence in TP0548 and TP0488 similar to subsp. pertenue and subsp. pallidum, respectively. PLoS Negl Trop Dis 2017; 11:e0005434. [PMID: 28263990 PMCID: PMC5354452 DOI: 10.1371/journal.pntd.0005434] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 03/16/2017] [Accepted: 02/23/2017] [Indexed: 11/25/2022] Open
Abstract
Background Treponema pallidum subsp. endemicum (TEN) is the causative agent of endemic syphilis (bejel). An unusual human TEN 11q/j isolate was obtained from a syphilis-like primary genital lesion from a patient that returned to France from Pakistan. Methodology/Principal findings The TEN 11q/j isolate was characterized using nested PCR followed by Sanger sequencing and/or direct Illumina sequencing. Altogether, 44 chromosomal regions were analyzed. Overall, the 11q/j isolate clustered with TEN strains Bosnia A and Iraq B as expected from previous TEN classification of the 11q/j isolate. However, the 11q/j sequence in a 505 bp-long region at the TP0488 locus was similar to Treponema pallidum subsp. pallidum (TPA) strains, but not to TEN Bosnia A and Iraq B sequences, suggesting a recombination event at this locus. Similarly, the 11q/j sequence in a 613 bp-long region at the TP0548 locus was similar to Treponema pallidum subsp. pertenue (TPE) strains, but not to TEN sequences. Conclusions/Significance A detailed analysis of two recombinant loci found in the 11q/j clinical isolate revealed that the recombination event occurred just once, in the TP0488, with the donor sequence originating from a TPA strain. Since TEN Bosnia A and Iraq B were found to contain TPA-like sequences at the TP0548 locus, the recombination at TP0548 took place in a treponeme that was an ancestor to both TEN Bosnia A and Iraq B. The sequence of 11q/j isolate in TP0548 represents an ancestral TEN sequence that is similar to yaws-causing treponemes. In addition to the importance of the 11q/j isolate for reconstruction of the TEN phylogeny, this case emphasizes the possible role of TEN strains in development of syphilis-like lesions. Treponema pallidum subsp. endemicum (TEN) is an uncultivable pathogenic treponeme that causes bejel (endemic syphilis), a chronic human infection mostly affecting children under 15 years of age, occurring mainly in several African and Middle East countries. In this work, we characterized a TEN 11q/j isolate from France that was obtained from an adult male with genital lesions, who was suspected of having syphilis and who received benzathine penicillin G. DNA sequencing of the isolate revealed two loci that were, rather than to TEN, related either to T. pallidum subsp. pertenue or to T. pallidum subsp. pallidum and likely resulted from recombination events. The recombination event in TP0488 as well as the recombination in TP0548, of the 11q/j, helped clarify the phylogeny of the TEN strains indicating that the recombination in TP0548 took place in a treponeme that was ancestral of Bosnia A and Iraq B, but was not an ancestor of the 11q/j isolate. In contrast, a recombination event in TP0488 appeared in the ancestor of the 11q/j isolate after separation of the ancestral treponeme of Bosnia A and Iraq B. This case also points to a possible role of TEN strains in development of syphilis-like lesions in countries with endemic syphilis.
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Affiliation(s)
- Lenka Mikalová
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Michal Strouhal
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Jan Oppelt
- CEITEC–Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Philippe Alain Grange
- Institut Cochin U1016, Laboratoire de Dermatologie—CNR Syphilis, Faculté de Médecine, Université Sorbonne Paris Descartes, Paris, France
| | - Michel Janier
- Centre des MST, Hôpital Saint-Louis, AP-HP, Paris, France
| | - Nadjet Benhaddou
- Institut Cochin U1016, Laboratoire de Dermatologie—CNR Syphilis, Faculté de Médecine, Université Sorbonne Paris Descartes, Paris, France
- Service de Bactériologie, Groupe Hospitalier Paris Centre Cochin-Hôtel Dieu-Broca, Paris, France
| | - Nicolas Dupin
- Institut Cochin U1016, Laboratoire de Dermatologie—CNR Syphilis, Faculté de Médecine, Université Sorbonne Paris Descartes, Paris, France
- Service de Dermatologie-Vénéréologie, Hôpital Cochin–Pavillon Tarnier, AP-HP, Paris, France
| | - David Šmajs
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
- * E-mail:
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Brautigam CA, Deka RK, Liu WZ, Norgard MV. The Tp0684 (MglB-2) Lipoprotein of Treponema pallidum: A Glucose-Binding Protein with Divergent Topology. PLoS One 2016; 11:e0161022. [PMID: 27536942 PMCID: PMC4990184 DOI: 10.1371/journal.pone.0161022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 06/24/2016] [Indexed: 11/18/2022] Open
Abstract
Treponema pallidum, the bacterium that causes syphilis, is an obligate human parasite. As such, it must acquire energy, in the form of carbon sources, from the host. There is ample evidence that the principal source of energy for this spirochete is D-glucose acquired from its environment, likely via an ABC transporter. Further, there is genetic evidence of a D-glucose chemotaxis system in T. pallidum. Both of these processes may be dependent on a single lipidated chemoreceptor: Tp0684, also called TpMglB-2 for its sequence homology to MglB of Escherichia coli. To broaden our understanding of this potentially vital protein, we determined a 2.05-Å X-ray crystal structure of a soluble form of the recombinant protein. Like its namesake, TpMglB-2 adopts a bilobed fold that is similar to that of the ligand-binding proteins (LBPs) of other ABC transporters. However, the protein has an unusual, circularly permuted topology. This feature prompted a series of biophysical studies that examined whether the protein's topological distinctiveness affected its putative chemoreceptor functions. Differential scanning fluorimetry and isothermal titration calorimetry were used to confirm that the protein bound D-glucose in a cleft between its two lobes. Additionally, analytical ultracentrifugation was employed to reveal that D-glucose binding is accompanied by a significant conformational change. TpMglB-2 thus appears to be fully functional in vitro, and given the probable central importance of the protein to T. pallidum's physiology, our results have implications for the viability and pathogenicity of this obligate human pathogen.
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Affiliation(s)
- Chad A. Brautigam
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States of America
| | - Ranjit K. Deka
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States of America
| | - Wei Z. Liu
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States of America
| | - Michael V. Norgard
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States of America
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Whole genome sequence of Treponema pallidum ssp. pallidum, strain Mexico A, suggests recombination between yaws and syphilis strains. PLoS Negl Trop Dis 2012; 6:e1832. [PMID: 23029591 PMCID: PMC3447947 DOI: 10.1371/journal.pntd.0001832] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 08/11/2012] [Indexed: 01/08/2023] Open
Abstract
Background Treponema pallidum ssp. pallidum (TPA), the causative agent of syphilis, and Treponema pallidum ssp. pertenue (TPE), the causative agent of yaws, are closely related spirochetes causing diseases with distinct clinical manifestations. The TPA Mexico A strain was isolated in 1953 from male, with primary syphilis, living in Mexico. Attempts to cultivate TPA Mexico A strain under in vitro conditions have revealed lower growth potential compared to other tested TPA strains. Methodology/Principal Findings The complete genome sequence of the TPA Mexico A strain was determined using the Illumina sequencing technique. The genome sequence assembly was verified using the whole genome fingerprinting technique and the final sequence was annotated. The genome size of the Mexico A strain was determined to be 1,140,038 bp with 1,035 predicted ORFs. The Mexico A genome sequence was compared to the whole genome sequences of three TPA (Nichols, SS14 and Chicago) and three TPE (CDC-2, Samoa D and Gauthier) strains. No large rearrangements in the Mexico A genome were found and the identified nucleotide changes occurred most frequently in genes encoding putative virulence factors. Nevertheless, the genome of the Mexico A strain, revealed two genes (TPAMA_0326 (tp92) and TPAMA_0488 (mcp2-1)) which combine TPA- and TPE- specific nucleotide sequences. Both genes were found to be under positive selection within TPA strains and also between TPA and TPE strains. Conclusions/Significance The observed mosaic character of the TPAMA_0326 and TPAMA_0488 loci is likely a result of inter-strain recombination between TPA and TPE strains during simultaneous infection of a single host suggesting horizontal gene transfer between treponemal subspecies. Treponema pallidum is a Gram-negative spirochete that causes diseases with distinct clinical manifestations and uses different transmission strategies. While syphilis (caused by subspecies pallidum) is a worldwide venereal and congenital disease, yaws (caused by subspecies pertenue) is a tropical disease transmitted by direct skin contact. Currently the genetic basis and evolution of these diseases remain unknown. In this study, we describe a high quality whole genome sequence of T. pallidum ssp. pallidum strain Mexico A, determined using the ?next generation? sequencing technique (Illumina). Although the genome of this strain contains no large rearrangements in comparison with other treponemal genomes, we found two genes which combined sequences from both subspecies pallidum and pertenue. The observed mosaic character of these two genes is likely a result of inter-strain recombination between pallidum and pertenue during simultaneous infection of a single host.
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Abstract
Syphilis is a chronic sexually transmitted disease caused by Treponema pallidum subsp. pallidum. Clinical manifestations separate the disease into stages; late stages of disease are now uncommon compared to the preantibiotic era. T. pallidum has an unusually small genome and lacks genes that encode many metabolic functions and classical virulence factors. The organism is extremely sensitive to environmental conditions and has not been continuously cultivated in vitro. Nonetheless, T. pallidum is highly infectious and survives for decades in the untreated host. Early syphilis lesions result from the host's immune response to the treponemes. Bacterial clearance and resolution of early lesions results from a delayed hypersensitivity response, although some organisms escape to cause persistent infection. One factor contributing to T. pallidum's chronicity is the paucity of integral outer membrane proteins, rendering intact organisms virtually invisible to the immune system. Antigenic variation of TprK, a putative surface-exposed protein, is likely to contribute to immune evasion. T. pallidum remains exquisitely sensitive to penicillin, but macrolide resistance has recently been identified in a number of geographic regions. The development of a syphilis vaccine, thus far elusive, would have a significant positive impact on global health.
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Affiliation(s)
- Rebecca E Lafond
- Department of Medicine, Box 359779, Harborview Medical Center, 325 Ninth Ave., Seattle, WA 98104, USA
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Deka RK, Goldberg MS, Hagman KE, Norgard MV. The Tp38 (TpMglB-2) lipoprotein binds glucose in a manner consistent with receptor function in Treponema pallidum. J Bacteriol 2004; 186:2303-8. [PMID: 15060032 PMCID: PMC412163 DOI: 10.1128/jb.186.8.2303-2308.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A 38-kDa lipoprotein of Treponema pallidum (Tp38) was predicted to be a periplasmic sugar-binding protein based on its sequence similarity to the glucose/galactose-binding (MglB) protein of Escherichia coli (P. S. Becker, D. R. Akins, J. D. Radolf, and M. V. Norgard, Infect. Immun. 62:1381-1391, 1994). Inasmuch as glucose is believed to be the principal, if not sole, carbon and energy source for T. pallidum and is readily available to the spirochete during its obligate infection of humans, we hypothesized that Tp38 may serve as the organism's requisite glucose receptor. For the present study, a nonacylated recombinant form of Tp38 was coexpressed with GroES and GroEL in E. coli to facilitate the isolation of soluble, properly folded Tp38. The highly sensitive method of intrinsic fluorescence spectroscopy, predicated on the manner in which tryptophan residues reside and move within protein microenvironments, was then used to assess sugar binding to Tp38. The intrinsic fluorescence of Tp38 was essentially unaltered when it was exposed to D-mannose, D-fucose, D-ribose, L-glucose, or L-galactose, but it changed markedly in the presence of D-glucose, and to a lesser extent, D-galactose, indicating binding. The K(d) values for D-glucose and D-galactose binding to Tp38 were 152.2 +/- 20.73 nM and 251.2 +/- 55.25 nM, respectively. Site-directed mutagenesis of Trp-145, a residue postulated to contribute to the sugar-binding pocket in a manner akin to the essential Trp-183 in E. coli MglB, abolished Tp38's conformational change in response to D-glucose. The combined data are consistent with Tp38 serving as a glucose receptor for T. pallidum. These findings potentially have important implications for syphilis pathogenesis, particularly as they may pertain to glucose-mediated chemotactic responses by T. pallidum.
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Affiliation(s)
- Ranjit K Deka
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Abstract
Chemotaxis transducers are specialized receptors that microorganisms use in order to sense the environment in directing their motility to favorable niches. The Escherichia coli transducers are models for studying the sensory and signaling events at the molecular level. Extensive studies in other organisms and the arrival of genomics has resulted in the accumulation of sequences of many transducer genes, but they are not fully understood. In silico analysis provides some assistance in classification of various transducers from different species and in predicting their function. All transducers contain two structural modules: a conserved C-terminal multidomain module, which is a signature element of the transducer superfamily, and a variable N-terminal module, which is responsible for the diversity within the superfamily. These structural modules have two distinct functions: the conserved C-terminal module is involved in signaling and adaptation, and the N-terminal module is involved in sensing various stimuli. Both C-terminal and N-terminal modules appear to be mobile genetic elements and subjects of duplication and lateral transfer. Although chemotaxis transducers are found exclusively in prokaryotic organisms that have some type of motility (flagellar, gliding or pili-based), several types of domains that are found in their N-terminal modules are also present in signal transduction proteins from eukaryotes, including humans. This indicates that basic principles of sensory transduction are conserved throughout the phylogenetic tree and that the chemotaxis transducer superfamily is a valuable source of novel sensory elements yet to be discovered.
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Affiliation(s)
- I B Zhulin
- School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, GA 30332-0230, USA.
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