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Mandal SK, Kanaujia SP. Structural and thermodynamic insights into a novel Mg 2+-citrate-binding protein from the ABC transporter superfamily. Acta Crystallogr D Struct Biol 2021; 77:1516-1534. [PMID: 34866608 DOI: 10.1107/s2059798321010457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/08/2021] [Indexed: 11/11/2022] Open
Abstract
More than one third of proteins require metal ions to accomplish their functions, making them obligatory for the growth and survival of microorganisms in varying environmental niches. In prokaryotes, besides their involvement in various cellular and physiological processes, metal ions stimulate the uptake of citrate molecules. Citrate is a source of carbon and energy and is reported to be transported by secondary transporters. In Gram-positive bacteria, citrate molecules are transported in complex with divalent metal ions, whereas in Gram-negative bacteria they are translocated by Na+/citrate symporters. In this study, the presence of a novel divalent-metal-ion-complexed citrate-uptake system that belongs to the primary active ABC transporter superfamily is reported. For uptake, the metal-ion-complexed citrate molecules are sequestered by substrate-binding proteins (SBPs) and transferred to transmembrane domains for their transport. This study reports crystal structures of an Mg2+-citrate-binding protein (MctA) from the Gram-negative thermophilic bacterium Thermus thermophilus HB8 in both apo and holo forms in the resolution range 1.63-2.50 Å. Despite binding various divalent metal ions, MctA possesses the coordination geometry to bind its physiological metal ion, Mg2+. The results also suggest an extended subclassification of cluster D SBPs, which are known to bind and transport divalent-metal-ion-complexed citrate molecules. Comparative assessment of the open and closed conformations of the wild-type and mutant MctA proteins suggests a gating mechanism of ligand entry following an `asymmetric domain movement' of the N-terminal domain for substrate binding.
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Affiliation(s)
- Suraj Kumar Mandal
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781 039, India
| | - Shankar Prasad Kanaujia
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781 039, India
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Radka CD, Aller SG. Site 2 of the Yersinia pestis substrate-binding protein YfeA is a dynamic surface metal-binding site. Acta Crystallogr F Struct Biol Commun 2021; 77:286-293. [PMID: 34473105 PMCID: PMC8411934 DOI: 10.1107/s2053230x21008086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 08/05/2021] [Indexed: 11/10/2022] Open
Abstract
The substrate-binding protein YfeA (also known as YPO2439 or y1897) is a polyspecific metal-binding protein that is crucial for nutrient acquisition and virulence in Yersinia pestis, the causative microbe of plague. YfeA folds into a monomeric c-clamp like other substrate-binding proteins and has two metal-binding sites (sites 1 and 2). Site 2 is a bidentate surface site capable of binding Zn and Mn atoms and is a unique feature of YfeA. Occasionally, the site 2 residues of two YfeA molecules will cooperate with the histidine tag of a third YfeA molecule in coordinating the same metal and lead to metal-dependent crystallographic packing. Here, three crystal structures of YfeA are presented at 1.85, 2.05 and 2.25 Å resolution. A comparison of the structures reveals that the metal can be displaced at five different locations ranging from ∼4 to ∼16 Å away from the canonical site 2. These observations reveal different configurations of site 2 that enable cooperative metal binding and demonstrate how site 2 is dynamic and freely available for inter-protein metal coordination.
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Affiliation(s)
- Christopher D. Radka
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Stephen G. Aller
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Abstract
The mammalian-cell-entry (Mce) proteins of Mycobacterium tuberculosis enable the bacterium to acquire lipids from the host cells. Asthana et al. [IUCrJ (2021). 8, 757-774] present the first structural insights into the potential assembly of Mce1 and Mce4, advancing our understanding of lipid transport by the human pathogen that causes tuberculosis.
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Affiliation(s)
- Ghader Bashiri
- Laboratory of Molecular and Microbial Biochemistry, School of Biological Sciences, The University of Auckland, Auckland 1010, New Zealand
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Asthana P, Singh D, Pedersen JS, Hynönen MJ, Sulu R, Murthy AV, Laitaoja M, Jänis J, Riley LW, Venkatesan R. Structural insights into the substrate-binding proteins Mce1A and Mce4A from Mycobacterium tuberculosis. IUCrJ 2021; 8:757-774. [PMID: 34584737 PMCID: PMC8420772 DOI: 10.1107/s2052252521006199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 06/15/2021] [Indexed: 05/28/2023]
Abstract
Mycobacterium tuberculosis (Mtb), which is responsible for more than a million deaths annually, uses lipids as the source of carbon and energy for its survival in the latent phase of infection. Mtb cannot synthesize all of the lipid molecules required for its growth and pathogenicity. Therefore, it relies on transporters such as the mammalian cell entry (Mce) complexes to import lipids from the host across the cell wall. Despite their importance for the survival and pathogenicity of Mtb, information on the structural properties of these proteins is not yet available. Each of the four Mce complexes in Mtb (Mce1-4) comprises six substrate-binding proteins (SBPs; MceA-F), each of which contains four conserved domains (N-terminal transmembrane, MCE, helical and C-terminal unstructured tail domains). Here, the properties of the various domains of Mtb Mce1A and Mce4A, which are involved in the import of mycolic/fatty acids and cholesterol, respectively, are reported. In the crystal structure of the MCE domain of Mce4A (MtMce4A39-140) a domain-swapped conformation is observed, whereas solution studies, including small-angle X-ray scattering (SAXS), indicate that all Mce1A and Mce4A domains are predominantly monomeric. Further, structural comparisons show interesting differences from the bacterial homologs MlaD, PqiB and LetB, which form homohexamers when assembled as functional transporter complexes. These data, and the fact that there are six SBPs in each Mtb mce operon, suggest that the MceA-F SBPs from Mce1-4 may form heterohexamers. Also, interestingly, the purification and SAXS analysis showed that the helical domains interact with the detergent micelle, suggesting that when assembled the helical domains of MceA-F may form a hydrophobic pore for lipid transport, as observed in EcPqiB. Overall, these data highlight the unique structural properties of the Mtb Mce SBPs.
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Affiliation(s)
- Pooja Asthana
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Dhirendra Singh
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Jan Skov Pedersen
- Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
| | - Mikko J. Hynönen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Ramita Sulu
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Abhinandan V. Murthy
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Mikko Laitaoja
- Department of Chemistry, University of Eastern Finland, Joensuu, Finland
| | - Janne Jänis
- Department of Chemistry, University of Eastern Finland, Joensuu, Finland
| | - Lee W. Riley
- School of Public Health, University of California, Berkeley, California, USA
| | - Rajaram Venkatesan
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
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de Boer M, Cordes T, Poolman B. Kinetic Modelling of Transport Inhibition by Substrates in ABC Importers. J Mol Biol 2020; 432:5565-5576. [PMID: 32800784 DOI: 10.1016/j.jmb.2020.08.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/05/2020] [Accepted: 08/09/2020] [Indexed: 12/11/2022]
Abstract
Prokaryotic ATP-binding cassette (ABC) importers require a substrate-binding protein (SBP) for the capture and delivery of the cognate substrate to the transmembrane domain (TMD) of the transporter. Various biochemical compounds have been identified that bind to the SBP but are not transported. The mechanistic basis for the "non-cognate" substrates not being transported differs. Some non-cognate substrates fail to trigger the appropriate conformational change in the SBP, resulting in loss of affinity for the TMD or the inability to allosterically activate transport. In another mechanism, the SBP cannot release the bound non-cognate substrate. Here, we used rate equations to derive the steady-state transport rate of cognate substrates of an ABC importer and investigated how non-cognate substrates influence this rate. We found that under limiting non-cognate substrate concentrations, the transport rate remains unaltered for each of the mechanisms. In contrast, at saturating substrate and SBP concentrations, the effect of the non-cognate substrate depends heavily on the respective mechanism. For instance, the transport rate becomes zero when the non-cognate substrate cannot be released by the SBP. Yet it remains unaffected when substrate release is possible but the SBP cannot dock onto the TMDs. Our work shows how the different mechanisms of substrate inhibition impact the transport kinetics, which is relevant for understanding and manipulating solute fluxes and hence the propagation of cells in nutritionally complex milieus.
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Affiliation(s)
- Marijn de Boer
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands; Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands.
| | - Thorben Cordes
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands; Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr, 2-4, 82152 Planegg-Martinsried, Germany
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands.
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Bernhard M, Diefenbach M, Biesalski M, Laube B. Electrical Sensing of Phosphonates by Functional Coupling of Phosphonate Binding Protein PhnD to Solid-State Nanopores. ACS Sens 2020; 5:234-241. [PMID: 31829017 DOI: 10.1021/acssensors.9b02097] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Combining the stability of solid-state nanopores with the unique sensing properties of biological components in a miniaturized electrical hybrid nanopore device is a challenging approach to advance the sensitivity and selectivity of small-molecule detection in healthcare and environment analytics. Here, we demonstrate a simple method to design an electrical hybrid nanosensor comprising a bacterial binding protein tethered to a solid-state nanopore allowing high-affinity detection of phosphonates. The diverse family of bacterial substrate-binding proteins (SBPs) binds specifically and efficiently to various substances and has been implicated as an ideal biorecognition element for analyte detection in the design of hybrid bionanosensors. Here, we demonstrate that the coupling of the purified phosphonate binding protein PhnD via primary amines to the reactive NHS groups of P(DMAA-co-NMAS) polymers inside a single track-etched nanopore in poly(ethylene terephthalate) (PET) foils results in ligand-specific and concentration-dependent changes in the nanopore current. Application of the phosphonate 2-aminoethylphosphonate (2AEP) or ethylphosphonate (EP) induces a large conformational rearrangement in PnhD around the hinge in a venus flytrap mechanism resulting in a concentration depended on increase of the single pore current with binding affinities of 27 and 373 nM, respectively. Thus, the specificity and stability of this simple hybrid sensor concept combine the advantages of both, the diversity of ligand-specific substrate-binding proteins and solid-state nanopores encouraging further options to produce robust devices amenable to medical or environmental high-throughput-based applications in nanotechnology.
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Affiliation(s)
- Max Bernhard
- Department of Biology, Neurophysiology and Neurosensory Systems, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Mathias Diefenbach
- Department of Chemistry, Laboratory of Macromolecular Chemistry and Paper Chemistry, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Markus Biesalski
- Department of Chemistry, Laboratory of Macromolecular Chemistry and Paper Chemistry, Alarich-Weiss-Str. 8, 64287 Darmstadt, Germany
| | - Bodo Laube
- Department of Biology, Neurophysiology and Neurosensory Systems, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
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Culurgioni S, Harris G, Singh AK, King SJ, Walsh MA. Structural Basis for Regulation and Specificity of Fructooligosaccharide Import in Streptococcus pneumoniae. Structure 2016; 25:79-93. [PMID: 27939783 PMCID: PMC5222590 DOI: 10.1016/j.str.2016.11.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 09/28/2016] [Accepted: 11/07/2016] [Indexed: 12/16/2022]
Abstract
Streptococcus pneumoniae is dependent on carbohydrate uptake for colonization and pathogenesis, and dedicates over a third of its transport systems to their uptake. The ability of the pneumococcus to utilize fructooligosaccharides (FOSs) is attributed to the presence of one of two types of FOS ATP-binding cassette (ABC) transporters. Strains encoding SfuABC are only able to utilize short-chain FOSs, while strains encoding FusABC can utilize both short- and long-chain FOSs. The crystal structures of the substrate-binding protein FusA in its open and closed conformations bound to FOSs, and solution scattering data of SfuA, delineate the structural basis for import of short- and long-chain FOSs. The structure of FusA identifies an EF hand-like calcium-binding motif. This is shown to be essential for translocation of FOSs in FusABC and forms the basis for the definition of a new class of substrate-binding proteins that regulate substrate translocation by calcium.
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Affiliation(s)
- Simone Culurgioni
- Diamond House, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK; Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot OX11 0FA, UK
| | - Gemma Harris
- Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot OX11 0FA, UK
| | - Anirudh K Singh
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Samantha J King
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Martin A Walsh
- Diamond House, Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK; Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot OX11 0FA, UK.
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