1
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Kröger P, Shanmugaratnam S, Scheib U, Höcker B. Fine-tuning spermidine binding modes in the putrescine binding protein PotF. J Biol Chem 2021; 297:101419. [PMID: 34801550 PMCID: PMC8666671 DOI: 10.1016/j.jbc.2021.101419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 11/10/2021] [Accepted: 11/12/2021] [Indexed: 11/09/2022] Open
Abstract
A profound understanding of the molecular interactions between receptors and ligands is important throughout diverse research, such as protein design, drug discovery, or neuroscience. What determines specificity and how do proteins discriminate against similar ligands? In this study, we analyzed factors that determine binding in two homologs belonging to the well-known superfamily of periplasmic binding proteins, PotF and PotD. Building on a previously designed construct, modes of polyamine binding were swapped. This change of specificity was approached by analyzing local differences in the binding pocket as well as overall conformational changes in the protein. Throughout the study, protein variants were generated and characterized structurally and thermodynamically, leading to a specificity swap and improvement in affinity. This dataset not only enriches our knowledge applicable to rational protein design but also our results can further lay groundwork for engineering of specific biosensors as well as help to explain the adaptability of pathogenic bacteria.
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Affiliation(s)
- Pascal Kröger
- Department for Biochemistry, University of Bayreuth, Bayreuth, Germany
| | - Sooruban Shanmugaratnam
- Department for Biochemistry, University of Bayreuth, Bayreuth, Germany; Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Ulrike Scheib
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Birte Höcker
- Department for Biochemistry, University of Bayreuth, Bayreuth, Germany; Max Planck Institute for Developmental Biology, Tübingen, Germany.
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2
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Herud-Sikimić O, Stiel AC, Kolb M, Shanmugaratnam S, Berendzen KW, Feldhaus C, Höcker B, Jürgens G. A biosensor for the direct visualization of auxin. Nature 2021; 592:768-772. [PMID: 33828298 PMCID: PMC8081663 DOI: 10.1038/s41586-021-03425-2] [Citation(s) in RCA: 75] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 03/05/2021] [Indexed: 01/03/2023]
Abstract
One of the most important regulatory small molecules in plants is indole-3-acetic acid, also known as auxin. Its dynamic redistribution has an essential role in almost every aspect of plant life, ranging from cell shape and division to organogenesis and responses to light and gravity1,2. So far, it has not been possible to directly determine the spatial and temporal distribution of auxin at a cellular resolution. Instead it is inferred from the visualization of irreversible processes that involve the endogenous auxin-response machinery3-7; however, such a system cannot detect transient changes. Here we report a genetically encoded biosensor for the quantitative in vivo visualization of auxin distribution. The sensor is based on the Escherichia coli tryptophan repressor8, the binding pocket of which is engineered to be specific to auxin. Coupling of the auxin-binding moiety with selected fluorescent proteins enables the use of a fluorescence resonance energy transfer signal as a readout. Unlike previous systems, this sensor enables direct monitoring of the rapid uptake and clearance of auxin by individual cells and within cell compartments in planta. By responding to the graded spatial distribution along the root axis and its perturbation by transport inhibitors-as well as the rapid and reversible redistribution of endogenous auxin in response to changes in gravity vectors-our sensor enables real-time monitoring of auxin concentrations at a (sub)cellular resolution and their spatial and temporal changes during the lifespan of a plant.
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Affiliation(s)
| | - Andre C Stiel
- Max Planck Institute for Developmental Biology, Tübingen, Germany
- Institute for Biological and Medical Imaging, Helmholtz Zentrum Munich, German Research Center for Environmental Health, Munich, Germany
| | - Martina Kolb
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Sooruban Shanmugaratnam
- Max Planck Institute for Developmental Biology, Tübingen, Germany
- Department of Biochemistry, University of Bayreuth, Bayreuth, Germany
| | - Kenneth W Berendzen
- Centre for Plant Molecular Biology, University of Tübingen, Tübingen, Germany
| | | | - Birte Höcker
- Max Planck Institute for Developmental Biology, Tübingen, Germany.
- Department of Biochemistry, University of Bayreuth, Bayreuth, Germany.
| | - Gerd Jürgens
- Max Planck Institute for Developmental Biology, Tübingen, Germany.
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3
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Deka RK, Liu WZ, Norgard MV, Brautigam CA. Biophysical and Biochemical Characterization of TP0037, a d-Lactate Dehydrogenase, Supports an Acetogenic Energy Conservation Pathway in Treponema pallidum. mBio 2020; 11:e02249-20. [PMID: 32963009 PMCID: PMC7512555 DOI: 10.1128/mbio.02249-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 08/18/2020] [Indexed: 12/13/2022] Open
Abstract
A longstanding conundrum in Treponema pallidum biology concerns how the spirochete generates sufficient energy to fulfill its complex pathogenesis processes during human syphilitic infection. For decades, it has been assumed that the bacterium relies solely on glucose catabolism (via glycolysis) for generation of its ATP. However, the organism's robust motility, believed to be essential for human tissue invasion and dissemination, would require abundant ATP likely not provided by the parsimony of glycolysis. As such, additional ATP generation, either via a chemiosmotic gradient, substrate-level phosphorylation, or both, likely exists in T. pallidum Along these lines, we have hypothesized that T. pallidum exploits an acetogenic energy conservation pathway that relies on the redox chemistry of flavins. Central to this hypothesis is the apparent existence in T. pallidum of an acetogenic pathway for the conversion of d-lactate to acetate. Herein we have characterized the structural, biophysical, and biochemical properties of the first enzyme (d-lactate dehydrogenase [d-LDH]; TP0037) predicted in this pathway. Binding and enzymatic studies showed that recombinant TP0037 consumed d-lactate and NAD+ to produce pyruvate and NADH. The crystal structure of TP0037 revealed a fold similar to that of other d-acid dehydrogenases; residues in the cofactor-binding and active sites were homologous to those of other known d-LDHs. The crystal structure and solution biophysical experiments revealed the protein's propensity to dimerize, akin to other d-LDHs. This study is the first to elucidate the enzymatic properties of T. pallidum's d-LDH, thereby providing new compelling evidence for a flavin-dependent acetogenic energy conservation (ATP-generating) pathway in T. pallidumIMPORTANCE Because T. pallidum lacks a Krebs cycle and the capability for oxidative phosphorylation, historically it has been difficult to reconcile how the syphilis spirochete generates sufficient ATP to fulfill its energy needs, particularly for its robust motility, solely from glycolysis. We have postulated the existence in T. pallidum of a flavin-dependent acetogenic energy conservation pathway that would generate additional ATP for T. pallidum bioenergetics. In the proposed acetogenic pathway, first d-lactate would be converted to pyruvate. Pyruvate would then be metabolized to acetate in three additional steps, with ATP being generated via substrate-level phosphorylation. This study provides structural, biochemical, and biophysical evidence for the first T. pallidum enzyme in the pathway (TP0037; d-lactate dehydrogenase) requisite for the conversion of d-lactate to pyruvate. The findings represent the first experimental evidence to support a role for an acetogenic energy conservation pathway that would contribute to nonglycolytic ATP production in T. pallidum.
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Affiliation(s)
- Ranjit K Deka
- Department of Microbiology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Wei Z Liu
- Department of Microbiology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Michael V Norgard
- Department of Microbiology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Chad A Brautigam
- Department of Microbiology, UT Southwestern Medical Center, Dallas, Texas, USA
- Department of Biophysics, UT Southwestern Medical Center, Dallas, Texas, USA
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4
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Luthra A, Montezuma-Rusca JM, La Vake CJ, LeDoyt M, Delgado KN, Davenport TC, Fiel-Gan M, Caimano MJ, Radolf JD, Hawley KL. Evidence that immunization with TP0751, a bipartite Treponema pallidum lipoprotein with an intrinsically disordered region and lipocalin fold, fails to protect in the rabbit model of experimental syphilis. PLoS Pathog 2020; 16:e1008871. [PMID: 32936831 PMCID: PMC7521688 DOI: 10.1371/journal.ppat.1008871] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 09/28/2020] [Accepted: 08/10/2020] [Indexed: 12/18/2022] Open
Abstract
Deconvolution of syphilis pathogenesis and selection of candidate syphilis vaccinogens requires detailed knowledge of the molecular architecture of the Treponema pallidum outer membrane (OM). The T. pallidum OM contains a low density of integral OM proteins, while the spirochete's many lipoprotein immunogens are periplasmic. TP0751, a lipoprotein with a lipocalin fold, is reportedly a surface-exposed protease/adhesin and protective antigen. The rapid expansion of calycin/lipocalin structures in the RCSB PDB database prompted a comprehensive reassessment of TP0751. Small angle X-ray scattering analysis of full-length protein revealed a bipartite topology consisting of an N-terminal, intrinsically disordered region (IDR) and the previously characterized C-terminal lipocalin domain. A DALI server query using the lipocalin domain yielded 97 hits, 52 belonging to the calycin superfamily, including 15 bacterial lipocalins, but no Gram-negative surface proteins. Surprisingly, Tpp17 (TP0435) was identified as a structural ortholog of TP0751. In silico docking predicted that TP0751 can bind diverse ligands along the rim of its eight-stranded β-barrel; high affinity binding of one predicted ligand, heme, to the lipocalin domain was demonstrated. qRT-PCR and immunoblotting revealed very low expression of TP0751 compared to other T. pallidum lipoproteins. Immunoblot analysis of immune rabbit serum failed to detect TP0751 antibodies, while only one of five patients with secondary syphilis mounted a discernible TP0751-specific antibody response. In opsonophagocytosis assays, neither TP0751 nor Tpp17 antibodies promoted uptake of T. pallidum by rabbit peritoneal macrophages. Rabbits immunized with intact, full-length TP0751 showed no protection against local or disseminated infection following intradermal challenge with T. pallidum. Our data argue that, like other lipoprotein lipocalins in dual-membrane bacteria, TP0751 is periplasmic and binds small molecules, and we propose that its IDR facilitates ligand binding by and offloading from the lipocalin domain. The inability of TP0751 to elicit opsonic or protective antibodies is consistent with a subsurface location.
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Affiliation(s)
- Amit Luthra
- Department of Medicine, UConn Health, Farmington, United States of America
| | - Jairo M. Montezuma-Rusca
- Department of Medicine, UConn Health, Farmington, United States of America
- Division of Infectious Diseases, UConn Health, Farmington, United States of America
- Department of Pediatrics, UConn Health, Farmington, United States of America
| | - Carson J. La Vake
- Department of Pediatrics, UConn Health, Farmington, United States of America
| | - Morgan LeDoyt
- Department of Medicine, UConn Health, Farmington, United States of America
| | | | | | - Mary Fiel-Gan
- Department of Pathology, Hartford Hospital, Hartford, United States of America
| | - Melissa J. Caimano
- Department of Medicine, UConn Health, Farmington, United States of America
- Department of Pediatrics, UConn Health, Farmington, United States of America
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, United States of America
| | - Justin D. Radolf
- Department of Medicine, UConn Health, Farmington, United States of America
- Department of Pediatrics, UConn Health, Farmington, United States of America
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, United States of America
- Department of Genetics and Genome Sciences, UConn Health, Farmington, United States of America
- Department of Immunology, UConn Health, Farmington, United States of America
| | - Kelly L. Hawley
- Department of Pediatrics, UConn Health, Farmington, United States of America
- Division of Infectious Diseases and Immunology, Connecticut Children’s, Hartford, United States of America
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5
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Abstract
The outer membrane (OM) of Treponema pallidum, the uncultivatable agent of venereal syphilis, has long been the subject of misconceptions and controversy. Decades ago, researchers postulated that T. pallidum's poor surface antigenicity is the basis for its ability to cause persistent infection, but they mistakenly attributed this enigmatic property to the presence of a protective outer coat of serum proteins and mucopolysaccharides. Subsequent studies revealed that the OM is the barrier to antibody binding, that it contains a paucity of integral membrane proteins, and that the preponderance of the spirochete's immunogenic lipoproteins is periplasmic. Since the advent of recombinant DNA technology, the fragility of the OM, its low protein content, and the lack of sequence relatedness between T. pallidum and Gram-negative outer membrane proteins (OMPs) have complicated efforts to characterize molecules residing at the host-pathogen interface. We have overcome these hurdles using the genomic sequence in concert with computational tools to identify proteins predicted to form β-barrels, the hallmark conformation of OMPs in double-membrane organisms and evolutionarily related eukaryotic organelles. We also have employed diverse methodologies to confirm that some candidate OMPs do, in fact, form amphiphilic β-barrels and are surface-exposed in T. pallidum. These studies have led to a structural homology model for BamA and established the bipartite topology of the T. pallidum repeat (Tpr) family of proteins. Recent bioinformatics has identified several structural orthologs for well-characterized Gram-negative OMPs, suggesting that the T. pallidum OMP repertoire is more Gram-negative-like than previously supposed. Lipoprotein adhesins and proteases on the spirochete surface also may contribute to disease pathogenesis and protective immunity.
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Affiliation(s)
- Justin D Radolf
- Departments of Medicine, Pediatrics, Molecular Biology and Biophysics, Genetics and Genomic Sciences, and Immunology, UConn Health, Farmington, CT 06030-3715, USA.
| | - Sanjiv Kumar
- Department of Medicine, UConn Health, Farmington, CT 06030-3715, USA
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6
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Houston S, Lithgow KV, Osbak KK, Kenyon CR, Cameron CE. Functional insights from proteome-wide structural modeling of Treponema pallidum subspecies pallidum, the causative agent of syphilis. BMC STRUCTURAL BIOLOGY 2018; 18:7. [PMID: 29769048 PMCID: PMC5956850 DOI: 10.1186/s12900-018-0086-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 04/27/2018] [Indexed: 12/21/2022]
Abstract
Background Syphilis continues to be a major global health threat with 11 million new infections each year, and a global burden of 36 million cases. The causative agent of syphilis, Treponema pallidum subspecies pallidum, is a highly virulent bacterium, however the molecular mechanisms underlying T. pallidum pathogenesis remain to be definitively identified. This is due to the fact that T. pallidum is currently uncultivatable, inherently fragile and thus difficult to work with, and phylogenetically distinct with no conventional virulence factor homologs found in other pathogens. In fact, approximately 30% of its predicted protein-coding genes have no known orthologs or assigned functions. Here we employed a structural bioinformatics approach using Phyre2-based tertiary structure modeling to improve our understanding of T. pallidum protein function on a proteome-wide scale. Results Phyre2-based tertiary structure modeling generated high-confidence predictions for 80% of the T. pallidum proteome (780/978 predicted proteins). Tertiary structure modeling also inferred the same function as primary structure-based annotations from genome sequencing pipelines for 525/605 proteins (87%), which represents 54% (525/978) of all T. pallidum proteins. Of the 175 T. pallidum proteins modeled with high confidence that were not assigned functions in the previously annotated published proteome, 167 (95%) were able to be assigned predicted functions. Twenty-one of the 175 hypothetical proteins modeled with high confidence were also predicted to exhibit significant structural similarity with proteins experimentally confirmed to be required for virulence in other pathogens. Conclusions Phyre2-based structural modeling is a powerful bioinformatics tool that has provided insight into the potential structure and function of the majority of T. pallidum proteins and helped validate the primary structure-based annotation of more than 50% of all T. pallidum proteins with high confidence. This work represents the first T. pallidum proteome-wide structural modeling study and is one of few studies to apply this approach for the functional annotation of a whole proteome. Electronic supplementary material The online version of this article (10.1186/s12900-018-0086-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Simon Houston
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Karen Vivien Lithgow
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | | | - Chris Richard Kenyon
- HIV/STI Unit, Institute of Tropical Medicine, Antwerp, Belgium.,Division of Infectious Diseases and HIV Medicine, University of Cape Town, Cape Town, South Africa
| | - Caroline E Cameron
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.
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7
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Wang M, Phanstiel O, von Kalm L. Evaluation of Polyamine Transport Inhibitors in a Drosophila Epithelial Model Suggests the Existence of Multiple Transport Systems. ACTA ACUST UNITED AC 2017; 5:medsci5040027. [PMID: 29135915 PMCID: PMC5753656 DOI: 10.3390/medsci5040027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 11/08/2017] [Accepted: 11/09/2017] [Indexed: 12/19/2022]
Abstract
Increased polyamine biosynthesis activity and an active polyamine transport system are characteristics of many cancer cell lines and polyamine depletion has been shown to be a viable anticancer strategy. Polyamine levels can be depleted by difluoromethylornithine (DFMO), an inhibitor of the key polyamine biosynthesis enzyme ornithine decarboxylase (ODC). However, malignant cells frequently circumvent DFMO therapy by up-regulating polyamine import. Therefore, there is a need to develop compounds that inhibit polyamine transport. Collectively, DFMO and a polyamine transport inhibitor (PTI) provide the basis for a combination therapy leading to effective intracellular polyamine depletion. We have previously shown that the pattern of uptake of a series of polyamine analogues in a Drosophila model epithelium shares many characteristics with mammalian cells, indicating a high degree of similarity between the mammalian and Drosophila polyamine transport systems. In this report, we focused on the utility of the Drosophila epithelial model to identify and characterize polyamine transport inhibitors. We show that a previously identified inhibitor of transport in mammalian cells has a similar activity profile in Drosophila. The Drosophila model was also used to evaluate two additional transport inhibitors. We further demonstrate that a cocktail of polyamine transport inhibitors is more effective than individual inhibitors, suggesting the existence of multiple transport systems in Drosophila. Our findings reinforce the similarity between the Drosophila and mammalian transport systems and the value of the Drosophila model to provide inexpensive early screening of molecules targeting the transport system.
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Affiliation(s)
- Minpei Wang
- Department of Biology, University of Central Florida, Orlando, FL 32816, USA.
| | - Otto Phanstiel
- Department of Medical Education, College of Medicine, University of Central Florida, Orlando, FL 32827, USA.
| | - Laurence von Kalm
- Department of Biology, University of Central Florida, Orlando, FL 32816, USA.
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8
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Olczak A, Cianci M. The signal-to-noise ratio in SAD experiments. CRYSTALLOGR REV 2017. [DOI: 10.1080/0889311x.2017.1386182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Andrzej Olczak
- Institute of General and Ecological Chemistry, Lodz University of Technology, Lodz, Poland
| | - Michele Cianci
- Department of Agricultural, Food and Environmental Sciences, Università Politecnica delle Marche, Ancona, Italy
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9
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Brautigam CA, Deka RK, Liu WZ, Tomchick DR, Norgard MV. Functional clues from the crystal structure of an orphan periplasmic ligand-binding protein from Treponema pallidum. Protein Sci 2017; 26:847-856. [PMID: 28168761 DOI: 10.1002/pro.3133] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 01/30/2017] [Accepted: 02/01/2017] [Indexed: 01/01/2023]
Abstract
The spirochete Treponema pallidum is the causative agent of syphilis, a sexually transmitted infection of major global importance. Other closely related subspecies of Treponema also are the etiological agents of the endemic treponematoses, such as yaws, pinta, and bejel. The inability of T. pallidum and its close relatives to be cultured in vitro has prompted efforts to characterize T. pallidum's proteins structurally and biophysically, particularly those potentially relevant to treponemal membrane biology, with the goal of possibly revealing the functions of those proteins. This report describes the structure of the treponemal protein Tp0737; this polypeptide has a fold characteristic of a class of periplasmic ligand-binding proteins associated with ABC-type transporters. Although no ligand for the protein was observed in electron-density maps, and thus the nature of the native ligand remains obscure, the structural data described herein provide a foundation for further efforts to elucidate the ligand and thus the function of this protein in T. pallidum.
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Affiliation(s)
- Chad A Brautigam
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390.,Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390
| | - Ranjit K Deka
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390
| | - Wei Z Liu
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390
| | - Diana R Tomchick
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390.,Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390
| | - Michael V Norgard
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390
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10
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Radolf JD, Deka RK, Anand A, Šmajs D, Norgard MV, Yang XF. Treponema pallidum, the syphilis spirochete: making a living as a stealth pathogen. Nat Rev Microbiol 2016; 14:744-759. [PMID: 27721440 DOI: 10.1038/nrmicro.2016.141] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The past two decades have seen a worldwide resurgence in infections caused by Treponema pallidum subsp. pallidum, the syphilis spirochete. The well-recognized capacity of the syphilis spirochete for early dissemination and immune evasion has earned it the designation 'the stealth pathogen'. Despite the many hurdles to studying syphilis pathogenesis, most notably the inability to culture and to genetically manipulate T. pallidum, in recent years, considerable progress has been made in elucidating the structural, physiological, and regulatory facets of T. pallidum pathogenicity. In this Review, we integrate this eclectic body of information to garner fresh insights into the highly successful parasitic lifestyles of the syphilis spirochete and related pathogenic treponemes.
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Affiliation(s)
- Justin D Radolf
- Departments of Medicine, Pediatrics, Genetics and Genomic Science, Molecular Biology and Biophysics, and Immunology, UConn Health, 263 Farmington Avenue, Farmington, Connecticut 06030-3715, USA
| | - Ranjit K Deka
- Department of Microbiology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9048, USA
| | - Arvind Anand
- Department of Medicine, UConn Health, 263 Farmington Avenue, Farmington, Connecticut 06030-3715, USA
| | - David Šmajs
- Department of Biology, Faculty of Medicine, Masaryk University, 625 00 Brno, Czech Republic
| | - Michael V Norgard
- Department of Microbiology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9048, USA
| | - X Frank Yang
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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11
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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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12
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Gorgel M, Bøggild A, Ulstrup JJ, Weiss MS, Müller U, Nissen P, Boesen T. Against the odds? De novo structure determination of a pilin with two cysteine residues by sulfur SAD. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:1095-101. [PMID: 25945575 DOI: 10.1107/s1399004715003272] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 02/16/2015] [Indexed: 11/11/2022]
Abstract
Exploiting the anomalous signal of the intrinsic S atoms to phase a protein structure is advantageous, as ideally only a single well diffracting native crystal is required. However, sulfur is a weak anomalous scatterer at the typical wavelengths used for X-ray diffraction experiments, and therefore sulfur SAD data sets need to be recorded with a high multiplicity. In this study, the structure of a small pilin protein was determined by sulfur SAD despite several obstacles such as a low anomalous signal (a theoretical Bijvoet ratio of 0.9% at a wavelength of 1.8 Å), radiation damage-induced reduction of the cysteines and a multiplicity of only 5.5. The anomalous signal was improved by merging three data sets from different volumes of a single crystal, yielding a multiplicity of 17.5, and a sodium ion was added to the substructure of anomalous scatterers. In general, all data sets were balanced around the threshold values for a successful phasing strategy. In addition, a collection of statistics on structures from the PDB that were solved by sulfur SAD are presented and compared with the data. Looking at the quality indicator R(anom)/R(p.i.m.), an inconsistency in the documentation of the anomalous R factor is noted and reported.
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Affiliation(s)
- Manuela Gorgel
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
| | - Andreas Bøggild
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
| | - Jakob Jensen Ulstrup
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
| | - Manfred S Weiss
- Macromolecular Crystallography (HZB-MX), Helmholtz Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Uwe Müller
- Macromolecular Crystallography (HZB-MX), Helmholtz Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Poul Nissen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
| | - Thomas Boesen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
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Zhao H, Piszczek G, Schuck P. SEDPHAT--a platform for global ITC analysis and global multi-method analysis of molecular interactions. Methods 2015; 76:137-148. [PMID: 25477226 PMCID: PMC4380758 DOI: 10.1016/j.ymeth.2014.11.012] [Citation(s) in RCA: 224] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 11/19/2014] [Accepted: 11/20/2014] [Indexed: 01/02/2023] Open
Abstract
Isothermal titration calorimetry experiments can provide significantly more detailed information about molecular interactions when combined in global analysis. For example, global analysis can improve the precision of binding affinity and enthalpy, and of possible linkage parameters, even for simple bimolecular interactions, and greatly facilitate the study of multi-site and multi-component systems with competition or cooperativity. A pre-requisite for global analysis is the departure from the traditional binding model, including an 'n'-value describing unphysical, non-integral numbers of sites. Instead, concentration correction factors can be introduced to account for either errors in the concentration determination or for the presence of inactive fractions of material. SEDPHAT is a computer program that embeds these ideas and provides a graphical user interface for the seamless combination of biophysical experiments to be globally modeled with a large number of different binding models. It offers statistical tools for the rigorous determination of parameter errors, correlations, as well as advanced statistical functions for global ITC (gITC) and global multi-method analysis (GMMA). SEDPHAT will also take full advantage of error bars of individual titration data points determined with the unbiased integration software NITPIC. The present communication reviews principles and strategies of global analysis for ITC and its extension to GMMA in SEDPHAT. We will also introduce a new graphical tool for aiding experimental design by surveying the concentration space and generating simulated data sets, which can be subsequently statistically examined for their information content. This procedure can replace the 'c'-value as an experimental design parameter, which ceases to be helpful for multi-site systems and in the context of gITC.
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Affiliation(s)
- Huaying Zhao
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - Grzegorz Piszczek
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter Schuck
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
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Scheuermann TH, Brautigam CA. High-precision, automated integration of multiple isothermal titration calorimetric thermograms: new features of NITPIC. Methods 2014; 76:87-98. [PMID: 25524420 DOI: 10.1016/j.ymeth.2014.11.024] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 11/15/2014] [Accepted: 11/17/2014] [Indexed: 11/25/2022] Open
Abstract
Isothermal titration calorimetry (ITC) has become a standard and widely available tool to measure the thermodynamic parameters of macromolecular associations. Modern applications of the method, including global analysis and drug screening, require the acquisition of multiple sets of data; sometimes these data sets number in the hundreds. Therefore, there is a need for quick, precise, and automated means to process the data, particularly at the first step of data analysis, which is commonly the integration of the raw data to yield an interpretable isotherm. Herein, we describe enhancements to an algorithm that previously has been shown to provide an automated, unbiased, and high-precision means to integrate ITC data. These improvements allow for the speedy and precise serial integration of an unlimited number of ITC data sets, and they have been implemented in the freeware program NITPIC, version 1.1.0. We present a comprehensive comparison of the performance of this software against an older version of NITPIC and a current version of Origin, which is commonly used for integration. The new methods recapitulate the excellent performance of the previous versions of NITPIC while speeding it up substantially, and their precision is significantly better than that of Origin. This new version of NITPIC is therefore well suited to the serial integration of many ITC data sets.
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Affiliation(s)
- Thomas H Scheuermann
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA
| | - Chad A Brautigam
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA.
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15
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Brautigam CA, Deka RK, Liu WZ, Norgard MV. Insights into the potential function and membrane organization of the TP0435 (Tp17) lipoprotein from Treponema pallidum derived from structural and biophysical analyses. Protein Sci 2014; 24:11-9. [PMID: 25287511 DOI: 10.1002/pro.2576] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 09/30/2014] [Indexed: 12/15/2022]
Abstract
The sexually transmitted disease syphilis is caused by the bacterial spirochete Treponema pallidum. This microorganism is genetically intractable, accounting for the large number of putative and undercharacterized members of the pathogen's proteome. In an effort to ascribe a function(s) to the TP0435 (Tp17) lipoprotein, we engineered a soluble variant of the protein (rTP0435) and determined its crystal structure at a resolution of 2.42 Å. The structure is characterized by an eight-stranded β-barrel protein with a shallow "basin" at one end of the barrel and an α-helix stacked on the opposite end. Furthermore, there is a disulfide-linked dimer of the protein in the asymmetric unit of the crystals. Solution hydrodynamic experiments established that purified rTP0435 is monomeric, but specifically forms the disulfide-stabilized dimer observed in the crystal structure. The data herein, when considered with previous work on TP0435, imply plausible roles for the protein in either ligand binding, treponemal membrane architecture, and/or pathogenesis.
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Affiliation(s)
- Chad A Brautigam
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, Texas, 75390
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16
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Scheib U, Shanmugaratnam S, Farías-Rico JA, Höcker B. Change in protein-ligand specificity through binding pocket grafting. J Struct Biol 2014; 185:186-92. [DOI: 10.1016/j.jsb.2013.06.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 05/03/2013] [Accepted: 06/04/2013] [Indexed: 12/26/2022]
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Brautigam CA, Deka RK, Norgard MV. Purification, crystallization and preliminary X-ray analysis of TP0435 (Tp17) from the syphilis spirochete Treponema pallidum. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:453-5. [PMID: 23545658 PMCID: PMC3614177 DOI: 10.1107/s1744309113006246] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 03/04/2013] [Indexed: 11/11/2022]
Abstract
Syphilis, caused by the bacterial spirochete Treponema pallidum, remains a prominent sexually transmitted infection worldwide. Despite sequencing of the genome of this obligate human pathogen 15 years ago, the functions of a large number of the gene products of T. pallidum are still unknown, particularly with respect to those of the organism's periplasmic lipoproteins. To better understand their functions, a structural biology approach has been pursued. To this end, the soluble portion of the T. pallidum TP0435 lipoprotein (also known as Tp17) was cloned, hyper-expressed in Escherichia coli and purified to apparent homogeneity. The protein crystals obtained from this preparation diffracted to 2.4 Å resolution and had the symmetry of space group R3. In the hexagonal setting, the unit-cell parameters were a = b = 85.7, c = 85.4 Å.
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Affiliation(s)
- Chad A Brautigam
- Department of Biophysics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
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Deka RK, Brautigam CA, Liu WZ, Tomchick DR, Norgard MV. The TP0796 lipoprotein of Treponema pallidum is a bimetal-dependent FAD pyrophosphatase with a potential role in flavin homeostasis. J Biol Chem 2013; 288:11106-21. [PMID: 23447540 DOI: 10.1074/jbc.m113.449975] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Treponema pallidum, an obligate parasite of humans and the causative agent of syphilis, has evolved the capacity to exploit host-derived metabolites for its survival. Flavin-containing compounds are essential cofactors that are required for metabolic processes in all living organisms, and riboflavin is a direct precursor of the cofactors FMN and FAD. Unlike many pathogenic bacteria, Treponema pallidum cannot synthesize riboflavin; we recently described a flavin-uptake mechanism composed of an ABC-type transporter. However, there is a paucity of information about flavin utilization in bacterial periplasms. Using a discovery-driven approach, we have identified the TP0796 lipoprotein as a previously uncharacterized Mg(2+)-dependent FAD pyrophosphatase within the ApbE superfamily. TP0796 probably plays a central role in flavin turnover by hydrolyzing exogenously acquired FAD, yielding AMP and FMN. Biochemical and structural investigations revealed that the enzyme has a unique bimetal Mg(2+) catalytic center. Furthermore, the pyrophosphatase activity is product-inhibited by AMP, indicating a possible role for this molecule in modulating FMN and FAD levels in the treponemal periplasm. The ApbE superfamily was previously thought to be involved in thiamine biosynthesis, but our characterization of TP0796 prompts a renaming of this superfamily as a periplasmic flavin-trafficking protein (Ftp). TP0796 is the first structurally and biochemically characterized FAD pyrophosphate enzyme in bacteria. This new paradigm for a bacterial flavin utilization pathway may prove to be useful for future inhibitor design.
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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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19
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Abstract
Bacterial transporter proteins are involved in the translocation of many essential nutrients and metabolites. However, many of these key bacterial transport systems remain to be identified, including those involved in the transport of riboflavin (vitamin B2). Pathogenic spirochetes lack riboflavin biosynthetic pathways, implying reliance on obtaining riboflavin from their hosts. Using structural and functional characterizations of possible ligand-binding components, we have identified an ABC-type riboflavin transport system within pathogenic spirochetes. The putative lipoprotein ligand-binding components of these systems from three different spirochetes were cloned, hyperexpressed in Escherichia coli, and purified to homogeneity. Solutions of all three of the purified recombinant proteins were bright yellow. UV-visible spectra demonstrated that these proteins were likely flavoproteins; electrospray ionization mass spectrometry and thin-layer chromatography confirmed that they contained riboflavin. A 1.3-Å crystal structure of the protein (TP0298) encoded by Treponema pallidum, the syphilis spirochete, demonstrated that the protein’s fold is similar to the ligand-binding components of ABC-type transporters. The structure also revealed other salient details of the riboflavin binding site. Comparative bioinformatics analyses of spirochetal genomes, coupled with experimental validation, facilitated the discovery of this new ABC-type riboflavin transport system(s). We denote the ligand-binding component as riboflavin uptake transporter A (RfuA). Taken together, it appears that pathogenic spirochetes have evolved an ABC-type transport system (RfuABCD) for survival in their host environments, particularly that of the human host. Syphilis remains a public health problem, but very little is known about the causative bacterium. This is because Treponema pallidum still cannot be cultured in the laboratory. Rather, T. pallidum must be cultivated in laboratory rabbits, a restriction that poses many insurmountable experimental obstacles. Approaches to learn more about the structure and function of T. pallidum’s cell envelope, which is both the physical and functional interface between T. pallidum and its human host, are severely limited. One approach for elucidating T. pallidum’s cell envelope has been to determine the three-dimensional structures of its membrane lipoproteins, molecules that serve many critical survival functions. Herein, we describe a previously unknown transport system that T. pallidum uses to import riboflavin, an essential nutrient for the organism’s survival. Moreover, we found that this transport system is present in other pathogenic spirochetes. This is the first description of this new type of bacterial riboflavin transport system.
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Biophysical and bioinformatic analyses implicate the Treponema pallidum Tp34 lipoprotein (Tp0971) in transition metal homeostasis. J Bacteriol 2012; 194:6771-81. [PMID: 23042995 DOI: 10.1128/jb.01494-12] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Metal ion homeostasis is a critical function of many integral and peripheral membrane proteins. The genome of the etiologic agent of syphilis, Treponema pallidum, is compact and devoid of many metabolic enzyme genes. Nevertheless, it harbors genes coding for homologs of several enzymes that typically require either iron or zinc. The product of the tp0971 gene of T. pallidum, designated Tp34, is a periplasmic lipoprotein that is thought to be tethered to the inner membrane of this organism. Previous work on a water-soluble (nonacylated) recombinant version of Tp34 established that this protein binds to Zn(2+), which, like other transition metal ions, stabilizes the dimeric form of the protein. In this study, we employed analytical ultracentrifugation to establish that four transition metal ions (Ni(2+), Co(2+), Cu(2+), and Zn(2+)) readily induce the dimerization of Tp34; Cu(2+) (50% effective concentration [EC(50)] = 1.7 μM) and Zn(2+) (EC(50) = 6.2 μM) were the most efficacious of these ions. Mutations of the crystallographically identified metal-binding residues hindered the ability of Tp34 to dimerize. X-ray crystallography performed on crystals of Tp34 that had been incubated with metal ions indicated that the binding site could accommodate the metals examined. The findings presented herein, coupled with bioinformatic analyses of related proteins, point to Tp34's likely role in metal ion homeostasis in T. pallidum.
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Brautigam CA, Deka RK, Schuck P, Tomchick DR, Norgard MV. Structural and thermodynamic characterization of the interaction between two periplasmic Treponema pallidum lipoproteins that are components of a TPR-protein-associated TRAP transporter (TPAT). J Mol Biol 2012; 420:70-86. [PMID: 22504226 DOI: 10.1016/j.jmb.2012.04.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/30/2012] [Accepted: 04/02/2012] [Indexed: 01/27/2023]
Abstract
Tripartite ATP-independent periplasmic transporters (TRAP-Ts) are bacterial transport systems that have been implicated in the import of small molecules into the cytoplasm. A newly discovered subfamily of TRAP-Ts [tetratricopeptide repeat-protein associated TRAP transporters (TPATs)] has four components. Three are common to both TRAP-Ts and TPATs: the P component, a ligand-binding protein, and a transmembrane symporter apparatus comprising the M and Q components (M and Q are sometimes fused to form a single polypeptide). TPATs are distinguished from TRAP-Ts by the presence of a unique protein called the "T component". In Treponema pallidum, this protein (TatT) is a water-soluble trimer whose protomers are each perforated by a pore. Its respective P component (TatP(T)) interacts with the TatT in vitro and in vivo. In this work, we further characterized this interaction. Co-crystal structures of two complexes between the two proteins confirm that up to three monomers of TatP(T) can bind to the TatT trimer. A putative ligand-binding cleft of TatP(T) aligns with the pore of TatT, strongly suggesting ligand transfer between T and P(T). We used a combination of site-directed mutagenesis and analytical ultracentrifugation to derive thermodynamic parameters for the interactions. These observations confirm that the observed crystallographic interface is recapitulated in solution. These results prompt a hypothesis of the molecular mechanism(s) of hydrophobic ligand transport by the TPATs.
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Affiliation(s)
- Chad A Brautigam
- Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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22
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Structural Basis of Substrate Binding Specificity Revealed by the Crystal Structures of Polyamine Receptors SpuD and SpuE from Pseudomonas aeruginosa. J Mol Biol 2012; 416:697-712. [DOI: 10.1016/j.jmb.2012.01.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 12/20/2011] [Accepted: 01/17/2012] [Indexed: 12/19/2022]
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Deka RK, Brautigam CA, Goldberg M, Schuck P, Tomchick DR, Norgard MV. Structural, bioinformatic, and in vivo analyses of two Treponema pallidum lipoproteins reveal a unique TRAP transporter. J Mol Biol 2012; 416:678-96. [PMID: 22306465 DOI: 10.1016/j.jmb.2012.01.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 12/15/2011] [Accepted: 01/11/2012] [Indexed: 01/22/2023]
Abstract
Treponema pallidum, the bacterial agent of syphilis, is predicted to encode one tripartite ATP-independent periplasmic transporter (TRAP-T). TRAP-Ts typically employ a periplasmic substrate-binding protein (SBP) to deliver the cognate ligand to the transmembrane symporter. Herein, we demonstrate that the genes encoding the putative TRAP-T components from T. pallidum, tp0957 (the SBP), and tp0958 (the symporter), are in an operon with an uncharacterized third gene, tp0956. We determined the crystal structure of recombinant Tp0956; the protein is trimeric and perforated by a pore. Part of Tp0956 forms an assembly similar to those of "tetratricopeptide repeat" (TPR) motifs. The crystal structure of recombinant Tp0957 was also determined; like the SBPs of other TRAP-Ts, there are two lobes separated by a cleft. In these other SBPs, the cleft binds a negatively charged ligand. However, the cleft of Tp0957 has a strikingly hydrophobic chemical composition, indicating that its ligand may be substantially different and likely hydrophobic. Analytical ultracentrifugation of the recombinant versions of Tp0956 and Tp0957 established that these proteins associate avidly. This unprecedented interaction was confirmed for the native molecules using in vivo cross-linking experiments. Finally, bioinformatic analyses suggested that this transporter exemplifies a new subfamily of TPATs (TPR-protein-associated TRAP-Ts) that require the action of a TPR-containing accessory protein for the periplasmic transport of a potentially hydrophobic ligand(s).
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Affiliation(s)
- Ranjit K Deka
- Department of Microbiology, The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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Yodsang P, Raksajit W, Brandt AM, Salminen TA, Mäenpää P, Incharoensakdi A. Recombinant polyamine-binding protein of Synechocystis sp. PCC 6803 specifically binds to and is induced by polyamines. BIOCHEMISTRY. BIOKHIMIIA 2011; 76:713-719. [PMID: 21639853 DOI: 10.1134/s0006297911060137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
His-tagged Synechocystis sp. PCC 6803 PotD protein (rPotD) involved in polyamine transport was overexpressed in Escherichia coli. The purified rPotD showed saturable binding kinetics with radioactively labeled polyamines. The rPotD exhibited a similar binding characteristic for three polyamines, with putrescine having less preference. The K(d) values for putrescine, spermine, and spermidine were 13.2, 8.3, and 7.8 µM, respectively. Binding of rPotD with polyamines was maximal at pH 8.0. Docking of these polyamines into the homology model of Synechocystis PotD showed that all three polyamines are able to interact with Synechocystis PotD. The binding modes of the docked putrescine and spermidine in Synechocystis are similar to those of PotF and PotD in E. coli, respectively. Competition experiments showed specific binding of rPotD with polyamines. The presence of putrescine and spermidine in the growth medium could induce an increase in PotD contents, suggesting the role of PotD in mediating the transport of polyamine in Synechocystis sp. PCC 6803.
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Affiliation(s)
- P Yodsang
- Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
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Eitinger T, Rodionov DA, Grote M, Schneider E. Canonical and ECF-type ATP-binding cassette importers in prokaryotes: diversity in modular organization and cellular functions. FEMS Microbiol Rev 2011; 35:3-67. [PMID: 20497229 DOI: 10.1111/j.1574-6976.2010.00230.x] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Thomas Eitinger
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
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Surface immunolabeling and consensus computational framework to identify candidate rare outer membrane proteins of Treponema pallidum. Infect Immun 2010; 78:5178-94. [PMID: 20876295 DOI: 10.1128/iai.00834-10] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Treponema pallidum reacts poorly with the antibodies present in rabbit and human syphilitic sera, a property attributed to the paucity of proteins in its outer membrane. To better understand the basis for the syphilis spirochete's "stealth pathogenicity," we used a dual-label, 3-step amplified assay in which treponemes encapsulated in gel microdroplets were probed with syphilitic sera in parallel with anti-FlaA antibodies. A small (approximately 5 to 10%) but reproducible fraction of intact treponemes bound IgG and/or IgM antibodies. Three lines of evidence supported the notion that the surface antigens were likely β-barrel-forming outer membrane proteins (OMPs): (i) surface labeling with anti-lipoidal (VDRL) antibodies was not observed, (ii) immunoblot analysis confirmed prior results showing that T. pallidum glycolipids are not immunoreactive, and (iii) labeling of intact organisms was not appreciably affected by proteinase K (PK) treatment. With this method, we also demonstrate that TprK (TP0897), an extensively studied candidate OMP, and TP0136, a lipoprotein recently reported to be surface exposed, are both periplasmic. Consistent with the immunolabeling studies, TprK was also found to lack amphiphilicity, a characteristic property of β-barrel-forming proteins. Using a consensus computational framework that combined subcellular localization and β-barrel structural prediction tools, we generated ranked groups of candidate rare OMPs, the predicted T. pallidum outer membrane proteome (OMPeome), which we postulate includes the surface-exposed molecules detected by our enhanced gel microdroplet assay. In addition to underscoring the syphilis spirochete's remarkably poor surface antigenicity, our findings help to explain the complex and shifting balance between pathogen and host defenses that characterizes syphilitic infection.
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Brandt AM, Raksajit W, Yodsang P, Mulo P, Incharoensakdi A, Salminen TA, Mäenpää P. Characterization of the substrate-binding PotD subunit in Synechocystis sp. strain PCC 6803. Arch Microbiol 2010; 192:791-801. [PMID: 20661547 DOI: 10.1007/s00203-010-0607-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 06/23/2010] [Accepted: 07/03/2010] [Indexed: 11/25/2022]
Abstract
The potD gene encodes the bacterial substrate-binding subunit of the polyamine transport system. The uptake system, which belongs to the ABC transporters, has been characterized in Escherichia coli, but it has not been previously studied in cyanobacteria. Although the overall sequence identity between Synechocystis sp. strain PCC 6803 (hereafter Synechocystis) PotD and Escherichia coli PotD is 24%, the ligand-binding site in the constructed homology model of Synechocystis PotD is well conserved. The conservation of the five polyamine-binding residues (Asp206, Glu209, Trp267, Trp293, and Asp295 in Synechocystis PotD) between these two species indicated polyamine-binding capacity for Synechocystis PotD. The Synechocystis potD gene is functional and its expression is under environmental regulation at transcriptional as well as post-transcriptional levels. Furthermore, an in vitro binding assay with the purified recombinant PotD protein demonstrated that the Synechocystis PotD protein is able to bind polyamines and favors spermidine over putrescine. Finally, we confirmed that Synechocystis PotD plays a physiological role in the uptake of polyamines in vivo using a constructed Synechocystis potD-disruption mutant.
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Borek D, Cymborowski M, Machius M, Minor W, Otwinowski Z. Diffraction data analysis in the presence of radiation damage. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:426-36. [PMID: 20382996 PMCID: PMC2852307 DOI: 10.1107/s0907444909040177] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Accepted: 10/02/2009] [Indexed: 11/10/2022]
Abstract
Radiation-induced decay of crystal diffraction and additional specific chemical changes of macromolecules forming the crystal lattice are currently two of the main limiting factors in the acquisition of macromolecular diffraction data and macromolecular structure determination. Data-processing and phasing protocols are discussed in the context of radiation-induced changes. In macromolecular crystallography, the acquisition of a complete set of diffraction intensities typically involves a high cumulative dose of X-ray radiation. In the process of data acquisition, the irradiated crystal lattice undergoes a broad range of chemical and physical changes. These result in the gradual decay of diffraction intensities, accompanied by changes in the macroscopic organization of crystal lattice order and by localized changes in electron density that, owing to complex radiation chemistry, are specific for a particular macromolecule. The decay of diffraction intensities is a well defined physical process that is fully correctable during scaling and merging analysis and therefore, while limiting the amount of diffraction, it has no other impact on phasing procedures. Specific chemical changes, which are variable even between different crystal forms of the same macromolecule, are more difficult to predict, describe and correct in data. Appearing during the process of data collection, they result in gradual changes in structure factors and therefore have profound consequences in phasing procedures. Examples of various combinations of radiation-induced changes are presented and various considerations pertinent to the determination of the best strategies for handling diffraction data analysis in representative situations are discussed.
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Affiliation(s)
- Dominika Borek
- University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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Valdés-Santiago L, Cervantes-Chávez JA, Ruiz-Herrera J. Ustilago maydisâspermidine synthase is encoded by a chimeric gene, required for morphogenesis, and indispensable for survival in the host. FEMS Yeast Res 2009; 9:923-35. [DOI: 10.1111/j.1567-1364.2009.00539.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Abstract
Treponema pallidum rapidly disseminates from a genital site of inoculation to diverse organs where it establishes persistent infection. T. pallidum has long been regarded as a stealth pathogen because of its poorly antigenic and non-inflammatory surface. There is now increasing evidence that antigenic variation also contributes to the ability of the spirochaete to evade host defences. Among the small number of proteins encoded by the T. pallidum genome with sequence similarity to well-characterized transcription factors is TP0262, an orthologue for cAMP regulatory protein (CRP) of Escherichia coli. Giacani and co-workers identified sequences matching the CRP consensus-binding motif upstream of the promoters of tprE, tprG and tprJ, three members of the T. pallidum repeat (tpr) gene family (subfamily II). Using electrophoretic mobility shift assay, DNaseI footprinting and an E. coli-based reporter system, they demonstrated that TP0262 specifically recognizes the putative binding sequences and that DNA binding is cAMP-dependent. Their report, a major methodological advance for syphilis research, suggests that T. pallidum has appropriated a paradigmatic global regulator of metabolic processes in heterotrophic bacteria to further its capacity for immune evasion in its obligate human host.
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Affiliation(s)
- Justin D Radolf
- Department of Medicine, University of Connecticut Health Centre, Farmington, CT 06030-3715, USA.
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Bjelić S, Jelesarov I. A survey of the year 2007 literature on applications of isothermal titration calorimetry. J Mol Recognit 2008; 21:289-312. [PMID: 18729242 DOI: 10.1002/jmr.909] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Elucidation of the energetic principles of binding affinity and specificity is a central task in many branches of current sciences: biology, medicine, pharmacology, chemistry, material sciences, etc. In biomedical research, integral approaches combining structural information with in-solution biophysical data have proved to be a powerful way toward understanding the physical basis of vital cellular phenomena. Isothermal titration calorimetry (ITC) is a valuable experimental tool facilitating quantification of the thermodynamic parameters that characterize recognition processes involving biomacromolecules. The method provides access to all relevant thermodynamic information by performing a few experiments. In particular, ITC experiments allow to by-pass tedious and (rarely precise) procedures aimed at determining the changes in enthalpy and entropy upon binding by van't Hoff analysis. Notwithstanding limitations, ITC has now the reputation of being the "gold standard" and ITC data are widely used to validate theoretical predictions of thermodynamic parameters, as well as to benchmark the results of novel binding assays. In this paper, we discuss several publications from 2007 reporting ITC results. The focus is on applications in biologically oriented fields. We do not intend a comprehensive coverage of all newly accumulated information. Rather, we emphasize work which has captured our attention with originality and far-reaching analysis, or else has provided ideas for expanding the potential of the method.
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Affiliation(s)
- Sasa Bjelić
- Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, Zürich, Switzerland
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