1
|
Takemiya K, Wang S, Liu Y, Murthy N, Goodman MM, Taylor WR. Isothermal titration calorimetry analysis of the binding between the maltodextrin binding protein malE of Staphylococcus aureus with maltodextrins of various lengths. Biochem Biophys Res Commun 2024; 695:149467. [PMID: 38211531 PMCID: PMC10842747 DOI: 10.1016/j.bbrc.2023.149467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 12/12/2023] [Accepted: 12/30/2023] [Indexed: 01/13/2024]
Abstract
Staphylococcus aureus (S. aureus), a Gram-positive bacterium, causes a wide range of infections, and diagnosis at an early stage is challenging. Targeting the maltodextrin transporter has emerged as a promising strategy for imaging bacteria and has been able to image a wide range of bacteria including S. aureus. However, little is known about the maltodextrin transporter in S. aureus, and this prevents new S. aureus specific ligands for the maltodextrin transporter from being developed. In Gram-positive bacteria, including S. aureus, the first step of maltodextrin transport is the binding of the maltodextrin-binding protein malE to maltodextrins. Thus, understanding the binding affinity and characteristics of malE from S. aureus is important to developing efficient maltodextrin-based imaging probes. We evaluated the affinity of malE of S. aureus to maltodextrins of various lengths. MalE of S. aureus (SAmalE) was expressed in E. coli BL21(DE3) and purified by Ni-NTA resin. The affinities of SAmalE to maltodextrins were evaluated with isothermal titration calorimetry. SAmalE has low affinity to maltose but binds to maltotriose and longer maltodextrins up to maltoheptaose with affinities up to Ka = 9.02 ± 0.49 × 105 M-1. SAmalE binding to maltotriose-maltoheptaose was exothermic and fit a single-binding site model. The van't Hoff enthalpy in the binding reaction of SAmalE with maltotriose was 9.9 ± 1.3 kcal/mol, and the highest affinity of SAmalE was observed with maltotetraose with Ka = 9.02 ± 0.49 × 105 M-1. In the plot of ΔH-T*ΔS, the of Enthalpy-Entropy Compensation effect was observed in binding reaction of SAmalE to maltodextrins. Acarbose and maltotetraiol bind with SAmalE indicating that SAmalE is tolerant of modifications on both the reducing and non-reducing ends of maltodextrins. Our results show that unlike ECmalE and similar to the maltodextrin binding protein of Streptococci, SAmalE primarily binds to maltodextrins via hydrogen bonds. This is distinct from the maltodextrin binding protein of Streptococci, SAmalE that binds to maltotetraiol with high affinity. Understanding the binding characteristics and tolerance to maltodextrins modifications by maltodextrin binding proteins will hopefully provide the basis for developing bacterial species-specific maltodextrin-based imaging probes.
Collapse
Affiliation(s)
- Kiyoko Takemiya
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, 1750 Haygood Dr. NE, Atlanta, GA, 30322, USA.
| | - Shelly Wang
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, 1750 Haygood Dr. NE, Atlanta, GA, 30322, USA
| | - Yu Liu
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, 1750 Haygood Dr. NE, Atlanta, GA, 30322, USA
| | - Niren Murthy
- Department of Bioengineering, Stanley Hall 306 University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Mark M Goodman
- Department of Radiology and Imaging Sciences, School of Medicine, Emory University, 1364 Clifton Road NE, Atlanta, GA, 30322, USA; Center for Systems Imaging, Emory University, 1364 Clifton Rd NE, Atlanta, 30322, Georgia
| | - W Robert Taylor
- Division of Cardiology, Department of Medicine, Emory University School of Medicine, 1750 Haygood Dr. NE, Atlanta, GA, 30322, USA; Joseph Maxwell Cleland Atlanta VA Medical Center, 1670 Clairmont Road, Decatur, GA, 30033, USA; Wallace H. Coulter Department of Biomedical Engineering School of Medicine, Emory University, 1750 Haygood Dr. NE, Atlanta, GA, 30322, USA
| |
Collapse
|
2
|
Zhao Y, Qin H, Yang YL, Li JQ, Qin SY, Zhang AQ, Lei X. Weakly aligned Ti 3C 2T x MXene liquid crystals: measuring residual dipolar coupling in multiple co-solvent systems. NANOSCALE 2023; 15:7820-7828. [PMID: 37051680 DOI: 10.1039/d3nr00204g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Residual Dipolar Coupling (RDC), acquired relying on weakly alignment media, is highly valuable for the structural elucidation of organic molecules. Arising from the striking features of no background signals and low critical concentrations, two-dimensional (2D) liquid crystals (LCs) show the clear advantages of acting as alignment media to measure RDCs. So far, creating multisolvent compatible 2D LC media through a simple and versatile method is still formidably challenging. Herein, we report the rapid creation of aligned media based on the Ti3C2Tx MXene, which self-aligned in multiple co-solvents including CH3OH-H2O, DMSO-H2O, DMF-H2O, and acetone-H2O. We demonstrated the applicability of these aligned media for the RDC measurement of small organic molecules with different polarities and solubilities. Notably, Ti3C2Tx MXene LCs without chemical modification enabled RDC measurements on aromatic molecules. The straightforward preparation of Ti3C2Tx media and its compatibility with multiple solvents will push RDC measurement as a routine methodology for structural elucidation. It may also facilitate the investigation of solvation effects on conformational dynamics.
Collapse
Affiliation(s)
- You Zhao
- Hubei Engineering Technology Research Centre of Energy Polymer Materials, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan 430074, China.
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education and Hubei Key Laboratory of Catalysis and Materials Science, South-Central Minzu University, Wuhan, China
| | - Huan Qin
- Hubei Engineering Technology Research Centre of Energy Polymer Materials, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan 430074, China.
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education and Hubei Key Laboratory of Catalysis and Materials Science, South-Central Minzu University, Wuhan, China
| | - Yan-Ling Yang
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, China.
| | - Jia-Qian Li
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, China.
| | - Si-Yong Qin
- Hubei Engineering Technology Research Centre of Energy Polymer Materials, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan 430074, China.
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education and Hubei Key Laboratory of Catalysis and Materials Science, South-Central Minzu University, Wuhan, China
| | - Ai-Qing Zhang
- Hubei Engineering Technology Research Centre of Energy Polymer Materials, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan 430074, China.
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education and Hubei Key Laboratory of Catalysis and Materials Science, South-Central Minzu University, Wuhan, China
| | - Xinxiang Lei
- School of Pharmaceutical Sciences, South-Central Minzu University, Wuhan, China.
| |
Collapse
|
3
|
Mächtel R, Narducci A, Griffith DA, Cordes T, Orelle C. An integrated transport mechanism of the maltose ABC importer. Res Microbiol 2019; 170:321-337. [PMID: 31560984 PMCID: PMC6906923 DOI: 10.1016/j.resmic.2019.09.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 09/10/2019] [Accepted: 09/13/2019] [Indexed: 12/27/2022]
Abstract
ATP-binding cassette (ABC) transporters use the energy of ATP hydrolysis to transport a large diversity of molecules actively across biological membranes. A combination of biochemical, biophysical, and structural studies has established the maltose transporter MalFGK2 as one of the best characterized proteins of the ABC family. MalF and MalG are the transmembrane domains, and two MalKs form a homodimer of nucleotide-binding domains. A periplasmic maltose-binding protein (MalE) delivers maltose and other maltodextrins to the transporter, and triggers its ATPase activity. Substrate import occurs in a unidirectional manner by ATP-driven conformational changes in MalK2 that allow alternating access of the substrate-binding site in MalF to each side of the membrane. In this review, we present an integrated molecular mechanism of the transport process considering all currently available information. Furthermore, we summarize remaining inconsistencies and outline possible future routes to decipher the full mechanistic details of transport by MalEFGK2 complex and that of related importer systems.
Collapse
Affiliation(s)
- Rebecca Mächtel
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Alessandra Narducci
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Douglas A Griffith
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Thorben Cordes
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany.
| | - Cédric Orelle
- Université de Lyon, CNRS, UMR5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 7 passage du Vercors, 69367 Lyon, France.
| |
Collapse
|
4
|
Licht A, Bommer M, Werther T, Neumann K, Hobe C, Schneider E. Structural and functional characterization of a maltose/maltodextrin ABC transporter comprising a single solute binding domain (MalE) fused to the transmembrane subunit MalF. Res Microbiol 2019; 170:1-12. [DOI: 10.1016/j.resmic.2018.08.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 08/15/2018] [Accepted: 08/28/2018] [Indexed: 01/21/2023]
|
5
|
Selmke B, Borbat PP, Nickolaus C, Varadarajan R, Freed JH, Trommer WE. Open and Closed Form of Maltose Binding Protein in Its Native and Molten Globule State As Studied by Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2018; 57:5507-5512. [PMID: 30004675 PMCID: PMC6211580 DOI: 10.1021/acs.biochem.8b00322] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An intensively investigated intermediate state of protein folding is the molten globule (MG) state, which contains secondary but hardly any tertiary structure. In previous work, we have determined the distances between interacting spins within maltose binding protein (MBP) in its native state using continuous wave and double electron-electron resonance (DEER) electron paramagnetic resonance (EPR) spectroscopy. Seven double mutants had been employed to investigate the structure within the two domains of MBP. DEER data nicely corroborated the previously available X-ray data. Even in its MG state, MBP is known to still bind its ligand maltose. We therefore hypothesized that there must be a defined structure around the binding pocket of MBP already in the absence of tertiary structure. Here we have investigated the functional and structural difference between native and MG state in the open and closed form with a new set of MBP mutants. In these, the spin-label positions were placed near the active site. Binding of its ligands leads to a conformational change from open to closed state, where the two domains are more closely together. The complete set of MBP mutants was analyzed at pH 3.2 (MG) and pH 7.4 (native state) using double-quantum coherence EPR. The values were compared with theoretical predictions of distances between the labels in biradicals constructed by molecular modeling from the crystal structures of MBP in open and closed form and were found to be in excellent agreement. Measurements show a defined structure around the binding pocket of MBP in MG, which explains maltose binding. A new and important finding is that in both states ligand-free MBP can be found in open and closed form, while ligand-bound MBP appears only in closed form because of maltose binding.
Collapse
Affiliation(s)
- Benjamin Selmke
- Department of Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern, Germany
| | - Peter P. Borbat
- Department of Chemistry and Chemical Biology, ACERT National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, NY 14853-1301, USA
| | - Chen Nickolaus
- Department of Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern, Germany
| | | | - Jack H. Freed
- Department of Chemistry and Chemical Biology, ACERT National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, NY 14853-1301, USA
| | - Wolfgang E. Trommer
- Department of Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern, Germany
| |
Collapse
|
6
|
Energy Coupling Efficiency in the Type I ABC Transporter GlnPQ. J Mol Biol 2018; 430:853-866. [PMID: 29432725 DOI: 10.1016/j.jmb.2018.02.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Revised: 01/28/2018] [Accepted: 02/01/2018] [Indexed: 01/29/2023]
Abstract
Solute transport via ATP binding cassette (ABC) importers involves receptor-mediated substrate binding, which is followed by ATP-driven translocation of the substrate across the membrane. How these steps are exactly initiated and coupled, and how much ATP it takes to complete a full transport cycle, are subject of debate. Here, we reconstitute the ABC importer GlnPQ in nanodiscs and in proteoliposomes and determine substrate-(in)dependent ATP hydrolysis and transmembrane transport. We determined the conformational states of the substrate-binding domains (SBDs) by single-molecule Förster resonance energy transfer measurements. We find that the basal ATPase activity (ATP hydrolysis in the absence of substrate) is mainly caused by the docking of the closed-unliganded state of the SBDs onto the transporter domain of GlnPQ and that, unlike glutamine, arginine binds both SBDs but does not trigger their closing. Furthermore, comparison of the ATPase activity in nanodiscs with glutamine transport in proteoliposomes shows that the stoichiometry of ATP per substrate is close to two. These findings help understand the mechanism of transport and the energy coupling efficiency in ABC transporters with covalently linked SBDs, which may aid our understanding of Type I ABC importers in general.
Collapse
|
7
|
Hsu WL, Furuta T, Sakurai M. The mechanism of nucleotide-binding domain dimerization in the intact maltose transporter as studied by all-atom molecular dynamics simulations. Proteins 2017; 86:237-247. [PMID: 29194754 DOI: 10.1002/prot.25433] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 11/09/2017] [Accepted: 11/27/2017] [Indexed: 11/12/2022]
Abstract
The Escherichia coli maltose transporter MalFGK2 -E belongs to the protein superfamily of ATP-binding cassette (ABC) transporters. This protein is composed of heterodimeric transmembrane domains (TMDs) MalF and MalG, and the homodimeric nucleotide-binding domains (NBDs) MalK2 . In addition to the TMDs and NBDs, the periplasmic maltose binding protein MalE captures maltose and shuttle it to the transporter. In this study, we performed all-atom molecular dynamics (MD) simulations on the maltose transporter and found that both the binding of MalE to the periplasmic side of the TMDs and binding of ATP to the MalK2 are necessary to facilitate the conformational change from the inward-facing state to the occluded state, in which MalK2 is completely dimerized. MalE binding suppressed the fluctuation of the TMDs and MalF periplasmic region (MalF-P2), and thus prevented the incorrect arrangement of the MalF C-terminal (TM8) helix. Without MalE binding, the MalF TM8 helix showed a tendency to intrude into the substrate translocation pathway, hindering the closure of the MalK2 . This observation is consistent with previous mutagenesis experimental results on MalF and provides a new point of view regarding the understanding of the substrate translocation mechanism of the maltose transporter.
Collapse
Affiliation(s)
- Wei-Lin Hsu
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Tadaomi Furuta
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Minoru Sakurai
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| |
Collapse
|
8
|
Lv D, Li C, Tan J, Zhang X, Wang C, Su J. Identification of functionally key residues in maltose transporter with an elastic network model-based thermodynamic method. Mol Phys 2016. [DOI: 10.1080/00268976.2016.1234077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Dashuai Lv
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Chunhua Li
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Jianjun Tan
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Xiaoyi Zhang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Cunxin Wang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, China
| | - Jiguo Su
- College of Science, Yanshan University, Qinhuangdao, China
| |
Collapse
|
9
|
Alvarez FJD, Orelle C, Huang Y, Bajaj R, Everly RM, Klug CS, Davidson AL. Full engagement of liganded maltose-binding protein stabilizes a semi-open ATP-binding cassette dimer in the maltose transporter. Mol Microbiol 2015; 98:878-94. [PMID: 26268698 DOI: 10.1111/mmi.13165] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2015] [Indexed: 01/31/2023]
Abstract
MalFGK2 is an ATP-binding cassette (ABC) transporter that mediates the uptake of maltose/maltodextrins into Escherichia coli. A periplasmic maltose-binding protein (MBP) delivers maltose to the transmembrane subunits (MalFG) and stimulates the ATPase activity of the cytoplasmic nucleotide-binding subunits (MalK dimer). This MBP-stimulated ATPase activity is independent of maltose for purified transporter in detergent micelles. However, when the transporter is reconstituted in membrane bilayers, only the liganded form of MBP efficiently stimulates its activity. To investigate the mechanism of maltose stimulation, electron paramagnetic resonance spectroscopy was used to study the interactions between the transporter and MBP in nanodiscs and in detergent. We found that full engagement of both lobes of maltose-bound MBP unto MalFGK2 is facilitated by nucleotides and stabilizes a semi-open MalK dimer. Maltose-bound MBP promotes the transition to the semi-open state of MalK when the transporter is in the membrane, whereas such regulation does not require maltose in detergent. We suggest that stabilization of the semi-open MalK2 conformation by maltose-bound MBP is key to the coupling of maltose transport to ATP hydrolysis in vivo, because it facilitates the progression of the MalK dimer from the open to the semi-open conformation, from which it can proceed to hydrolyze ATP.
Collapse
Affiliation(s)
| | - Cédric Orelle
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Yan Huang
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Ruchika Bajaj
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - R Michael Everly
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Candice S Klug
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Amy L Davidson
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| |
Collapse
|
10
|
Pistolesi S, Tjandra N, Bermejo GA. Solution NMR studies of periplasmic binding proteins and their interaction partners. Biomol Concepts 2015; 2:53-64. [PMID: 25962019 DOI: 10.1515/bmc.2011.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Periplasmic binding proteins (PBPs) are a crucial part of ATP-binding cassette import systems in Gram-negative bacteria. Central to their function is the ability to undergo a large-scale conformational rearrangement from open-unliganded to closed-liganded, which signals the presence of substrate and starts its translocation. Over the years, PBPs have been extensively studied not only owing to their essential role in nutrient uptake but also because they serve as excellent models for both practical applications (e.g., biosensor technology) and basic research (e.g., allosteric mechanisms). Although much of our knowledge at atomic level has been inferred from the detailed, static pictures afforded by crystallographic studies, nuclear magnetic resonance (NMR) has been able to fill certain gaps in such body of work, particularly with regard to dynamic processes. Here, we review NMR studies on PBPs, and their unique insights on conformation, dynamics, energetics, substrate binding, and interactions with related transport proteins. Based on the analysis of recent paramagnetic NMR results, as well as crystallographic and functional observations, we propose a mechanism that could explain the ability of certain PBPs to achieve a closed conformation in absence of ligand while others seem to remain open until ligand-mediated closure.
Collapse
|
11
|
Abstract
ATP-binding cassette transporters are multi-subunit membrane pumps that transport substrates across membranes. While significant in the transport process, transporter architecture exhibits a range of diversity that we are only beginning to recognize. This divergence may provide insight into the mechanisms of substrate transport and homeostasis. Until recently, ABC importers have been classified into two types, but with the emergence of energy-coupling factor (ECF) transporters there are potentially three types of ABC importers. In this review, we summarize an expansive body of research on the three types of importers with an emphasis on the basics that underlie ABC importers, such as structure, subunit composition and mechanism.
Collapse
Affiliation(s)
- Austin J Rice
- Department of Molecular Biosciences, Northwestern University , Evanston, IL , USA
| | | | | |
Collapse
|
12
|
Li CH, Yang YX, Su JG, Liu B, Tan JJ, Zhang XY, Wang CX. Allosteric transitions of the maltose transporter studied by an elastic network model. Biopolymers 2014; 101:758-68. [DOI: 10.1002/bip.22455] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 12/02/2013] [Accepted: 12/09/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Chun Hua Li
- College of Life Science and Bioengineering; Beijing University of Technology; Beijing 100124 China
| | - Yong Xiao Yang
- College of Life Science and Bioengineering; Beijing University of Technology; Beijing 100124 China
| | - Ji Guo Su
- College of Science; Yanshan University; Qinhuangdao 066004 China
| | - Bin Liu
- College of Life Science and Bioengineering; Beijing University of Technology; Beijing 100124 China
| | - Jian Jun Tan
- College of Life Science and Bioengineering; Beijing University of Technology; Beijing 100124 China
| | - Xiao Yi Zhang
- College of Life Science and Bioengineering; Beijing University of Technology; Beijing 100124 China
| | - Cun Xin Wang
- College of Life Science and Bioengineering; Beijing University of Technology; Beijing 100124 China
| |
Collapse
|
13
|
Sippach M, Weidlich D, Klose D, Abé C, Klare J, Schneider E, Steinhoff HJ. Conformational changes of the histidine ATP-binding cassette transporter studied by double electron-electron resonance spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1760-8. [PMID: 24583084 DOI: 10.1016/j.bbamem.2014.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 02/06/2014] [Accepted: 02/18/2014] [Indexed: 10/25/2022]
Abstract
The conformational dynamics of the histidine ABC transporter HisQMP2 from Salmonella enterica serovar Typhimurium, reconstituted into liposomes, is studied by site-directed spin labeling and double electron-electron resonance spectroscopy in the absence of nucleotides, in the ATP-bound, and in the post-hydrolysis state. The results show that the inter-dimer distances as measured between the Q-loops of HisP2 in the intact transporter resemble those determined for the maltose transporter in all three states of the hydrolysis cycle. Only in the presence of liganded HisJ the closed conformation of the nucleotide binding sites is achieved revealing the transmembrane communication of the presence of substrate. Two conformational states can be distinguished for the periplasmic moiety of HisQMP2 as detected by differences in distributions of interspin distances between positions 86 and 96 or 104 and 197. The observed conformational changes are correlated to proposed open, semi-open and closed conformations of the nucleotide binding domains HisP2. Our results are in line with a rearrangement of transmembrane helices 4 and 4' of HisQM during the closed to the semi-open transition of HisP2 driven by the reorientation of the coupled helices 3a and 3b to occur upon hydrolysis.
Collapse
Affiliation(s)
- Michael Sippach
- Fachbereich Physik, Universität Osnabrück, Barbarastr.7, 49076 Osnabrück, Germany
| | - Daniela Weidlich
- Institut für Biologie, AG Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany
| | - Daniel Klose
- Fachbereich Physik, Universität Osnabrück, Barbarastr.7, 49076 Osnabrück, Germany
| | - Christoph Abé
- Fachbereich Physik, Universität Osnabrück, Barbarastr.7, 49076 Osnabrück, Germany
| | - Johann Klare
- Fachbereich Physik, Universität Osnabrück, Barbarastr.7, 49076 Osnabrück, Germany
| | - Erwin Schneider
- Institut für Biologie, AG Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany
| | | |
Collapse
|
14
|
The Maltose ABC Transporter: Where Structure Meets Function. SPRINGER SERIES IN BIOPHYSICS 2014. [DOI: 10.1007/978-3-642-53839-1_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
15
|
Chu BCH, DeWolf T, Vogel HJ. Role of the two structural domains from the periplasmic Escherichia coli histidine-binding protein HisJ. J Biol Chem 2013; 288:31409-22. [PMID: 24036119 DOI: 10.1074/jbc.m113.490441] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Escherichia coli HisJ is a type II periplasmic binding protein that functions to reversibly capture histidine and transfer it to its cognate inner membrane ABC permease. Here, we used NMR spectroscopy to determine the structure of apo-HisJ (26.5 kDa) in solution. HisJ is a bilobal protein in which domain 1 (D1) is made up of two noncontiguous subdomains, and domain 2 (D2) is expressed as the inner domain. To better understand the roles of D1 and D2, we have isolated and characterized each domain separately. Structurally, D1 closely resembles its homologous domain in apo- and holo-HisJ, whereas D2 is more similar to the holo-form. NMR relaxation experiments reveal that HisJ becomes more ordered upon ligand binding, whereas isolated D2 experiences a significant reduction in slower (millisecond to microsecond) motions compared with the homologous domain in apo-HisJ. NMR titrations reveal that D1 is able to bind histidine in a similar manner as full-length HisJ, albeit with lower affinity. Unexpectedly, isolated D1 and D2 do not interact with each other in the presence or absence of histidine, which indicates the importance of intact interdomain-connecting elements (i.e. hinge regions) for HisJ functioning. Our results shed light on the binding mechanism of type II periplasmic binding proteins where ligand is initially bound by D1, and D2 plays a supporting role in this dynamic process.
Collapse
Affiliation(s)
- Byron C H Chu
- From the Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Alberta T2N 1N4, Canada
| | | | | |
Collapse
|
16
|
Tseng CW, Kanci A, Citti C, Rosengarten R, Chiu CJ, Chen ZH, Geary SJ, Browning GF, Markham PF. MalF is essential for persistence of Mycoplasma gallisepticum in vivo. MICROBIOLOGY-SGM 2013; 159:1459-1470. [PMID: 23657682 DOI: 10.1099/mic.0.067553-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
There is limited understanding of the molecular basis of virulence in the important avian pathogen Mycoplasma gallisepticum. To define genes that may be involved in colonization of chickens, a collection of mutants of the virulent Ap3AS strain of M. gallisepticum were generated by signature-tagged transposon mutagenesis. The collection included mutants with single insertions in the genes encoding the adhesin GapA and the cytadherence-related protein CrmA, and Western blotting confirmed that these mutants did not express these proteins. In two separate in vivo screenings, two GapA-deficient mutants (ST mutants 02-1 and 06-1) were occasionally recovered from birds, suggesting that GapA expression may not always be essential for persistence of strain Ap3AS. CrmA-deficient ST mutant 33-1 colonized birds poorly and had reduced virulence, indicating that CrmA was a significant virulence factor, but was not absolutely essential for colonization. ST mutant 04-1 contained a single transposon insertion in malF, a predicted ABC sugar transport permease, and could not be reisolated even when inoculated by itself into a group of birds, suggesting that expression of MalF was essential for persistence of M. galliseptium strain Ap3AS in infected birds.
Collapse
Affiliation(s)
- Chi-Wen Tseng
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Anna Kanci
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Christine Citti
- Institute of Bacteriology, Mycology and Hygiene, University of Veterinary Medicine, Vienna, A-1210 Vienna, Austria.,INRA, ENVT, UMR 1225, 31076 Toulouse, France
| | - Renate Rosengarten
- Institute of Bacteriology, Mycology and Hygiene, University of Veterinary Medicine, Vienna, A-1210 Vienna, Austria
| | - Chien-Ju Chiu
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Zheng-Hong Chen
- Microbiology Department, Basic Medical College, Guiyang Medical University, Guiyang, Guizhou 550004, PR China
| | - Steven J Geary
- Center of Excellence for Vaccine Research, Department of Pathobiology and Veterinary Science, The University of Connecticut, Storrs, Connecticut 06269, USA
| | - Glenn F Browning
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Philip F Markham
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia
| |
Collapse
|
17
|
Bodelón G, Palomino C, Fernández LÁ. Immunoglobulin domains inEscherichia coliand other enterobacteria: from pathogenesis to applications in antibody technologies. FEMS Microbiol Rev 2013; 37:204-50. [DOI: 10.1111/j.1574-6976.2012.00347.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 06/07/2012] [Accepted: 06/14/2012] [Indexed: 11/28/2022] Open
|
18
|
Jacso T, Schneider E, Rupp B, Reif B. Substrate transport activation is mediated through second periplasmic loop of transmembrane protein MalF in maltose transport complex of Escherichia coli. J Biol Chem 2012; 287:17040-17049. [PMID: 22451670 DOI: 10.1074/jbc.m112.340679] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In a recent study we described the second periplasmic loop P2 of the transmembrane protein MalF (MalF-P2) of the maltose ATP-binding cassette transporter (MalFGK(2)-E) as an important element in the recognition of substrate by the maltose-binding protein MalE. In this study, we focus on MalE and find that MalE undergoes a structural rearrangement after addition of MalF-P2. Analysis of residual dipolar couplings (RDCs) shows that binding of MalF-P2 induces a semiopen state of MalE in the presence and absence of maltose, whereas maltose is retained in the binding pocket. These data are in agreement with paramagnetic relaxation enhancement experiments. After addition of MalF-P2, an increased solvent accessibility for residues in the vicinity of the maltose-binding site of MalE is observed. MalF-P2 is thus not only responsible for substrate recognition, but also directly involved in activation of substrate transport. The observation that substrate-bound and substrate-free MalE in the presence of MalF-P2 adopts a similar semiopen state hints at the origin of the futile ATP hydrolysis of MalFGK(2)-E.
Collapse
Affiliation(s)
- Tomas Jacso
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany; Helmholtz-Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany
| | - Erwin Schneider
- Institut für Biologie, AG Bakterienphysiologie, Humboldt-Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany
| | - Bernd Rupp
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany
| | - Bernd Reif
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany; Helmholtz-Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany; Center for Integrated Protein Science Munich at Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
| |
Collapse
|
19
|
Wei X, Guo Y, Shao C, Sun Z, Zhurina D, Liu D, Liu W, Zou D, Jiang Z, Wang X, Zhao J, Shang W, Li X, Liao X, Huang L, Riedel CU, Yuan J. Fructose uptake in Bifidobacterium longum NCC2705 is mediated by an ATP-binding cassette transporter. J Biol Chem 2011; 287:357-367. [PMID: 22102285 DOI: 10.1074/jbc.m111.266213] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, a putative ATP-binding cassette (ABC) transport system was identified in Bifidobacterium longum NCC2705 that is highly up-regulated during growth on fructose as the sole carbon source. Cloning and expression of the corresponding ORFs (bl0033-0036) result in efficient fructose uptake by bacteria. Sequence analysis reveals high similarity to typical ABC transport systems and suggests that these genes are organized as an operon. Expression of FruE is induced by fructose, ribose, or xylose and is able to bind these sugars with fructose as the preferred substrate. Our data suggest that BL0033-0036 constitute a high affinity fructose-specific ABC transporter of B. longum NCC2705. We thus suggest to rename the coding genes to fruEKFG and the corresponding proteins to FruE (sugar-binding protein), FruK (ATPase subunit), FruF, and FruG (membrane permeases). Furthermore, protein-protein interactions between the components of the transporter complex were determined by GST pulldown and Western blot analysis. This revealed interactions between the membrane subunits FruF and FruG with FruE, which in vivo is located on the external side of the membrane, and with the cytoplasmatic ATPase FruK. This is in line with the proposed model for bacterial ABC sugar transporters.
Collapse
Affiliation(s)
- Xiao Wei
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Yanhong Guo
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China; School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Changlin Shao
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China; School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Zhongke Sun
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China; Institute of Microbiology and Biotechnology, University of Ulm, Ulm D-89069, Germany
| | - Daria Zhurina
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm D-89069, Germany
| | - Dawei Liu
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Wei Liu
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Dayang Zou
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Zheng Jiang
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Xuesong Wang
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Jiangli Zhao
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Wei Shang
- School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xuelian Li
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Xiangru Liao
- School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Liuyu Huang
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China.
| | - Christian U Riedel
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm D-89069, Germany.
| | - Jing Yuan
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China.
| |
Collapse
|
20
|
Schneider E, Eckey V, Weidlich D, Wiesemann N, Vahedi-Faridi A, Thaben P, Saenger W. Receptor-transporter interactions of canonical ATP-binding cassette import systems in prokaryotes. Eur J Cell Biol 2011; 91:311-7. [PMID: 21561685 DOI: 10.1016/j.ejcb.2011.02.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/15/2011] [Accepted: 02/15/2011] [Indexed: 02/07/2023] Open
Abstract
ATP-binding cassette (ABC) transport systems mediate the translocation of solutes across biological membranes at the expense of ATP. They share a common modular architecture comprising two pore-forming transmembrane domains and two nucleotide binding domains. In prokaryotes, ABC transporters are involved in the uptake of a large variety of chemicals, including nutrients, osmoprotectants and signal molecules. In pathogenic bacteria, some ABC importers are virulence factors. Canonical ABC import systems require an additional component, a substrate-specific receptor or binding protein for function. Interaction of the liganded receptor with extracytoplasmic loop regions of the transmembrane domains initiate the transport cycle. In this review we summarize the current knowledge on receptor-transporter interplay provided by crystal structures as well as by biochemical and biophysical means. In particular, we focus on the maltose/maltodextrin transporter of enterobacteria and the transporters for positively charged amino acids from the thermophile Geobacillus stearothermophilus and Salmonella enterica serovar Typhimurium.
Collapse
Affiliation(s)
- Erwin Schneider
- Institut für Biologie, AG Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany.
| | | | | | | | | | | | | |
Collapse
|
21
|
Cui J, Qasim S, Davidson AL. Uncoupling substrate transport from ATP hydrolysis in the Escherichia coli maltose transporter. J Biol Chem 2010; 285:39986-93. [PMID: 20959448 DOI: 10.1074/jbc.m110.147819] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the ATP-binding cassette superfamily couple the energy from ATP hydrolysis to the active transport of substrates across the membrane. The maltose transporter, a well characterized model system, consists of a periplasmic maltose-binding protein (MBP) and a multisubunit membrane transporter, MalFGK(2). On the basis of the structure of the MBP-MalFGK(2) complex in an outward-facing conformation (Oldham, M. L., Khare, D., Quiocho, F. A., Davidson, A. L., and Chen, J. (2007) Nature 450, 515-521), we identified two mutants in transmembrane domains MalF and MalG that generated futile cycling; although interaction with MBP stimulated the ATPase activity of the transporter, maltose was not transported. Both mutants appeared to disrupt the normal transfer of maltose from MBP to MalFGK(2). In the first case, substitution of aspartate for glycine in the maltose-binding site of MalF likely generated a futile cycle by preventing maltose from binding to MalFGK(2) during the catalytic cycle. In the second case, a four-residue deletion of a periplasmic loop of MalG limited its reach into the maltose-binding pocket of MBP, allowing maltose to remain associated with MBP during the catalytic cycle. Retention of maltose in the MBP binding site in the deletion mutant, as well as insertion of this loop into the binding site in the wild type, was detected by EPR as a change in mobility of a nitroxide spin label positioned near the maltose-binding pocket of MBP.
Collapse
Affiliation(s)
- Jinming Cui
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
| | | | | |
Collapse
|
22
|
Bordignon E, Grote M, Schneider E. The maltose ATP-binding cassette transporter in the 21st century - towards a structural dynamic perspective on its mode of action. Mol Microbiol 2010; 77:1354-66. [PMID: 20659291 DOI: 10.1111/j.1365-2958.2010.07319.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Enrica Bordignon
- ETH Zurich, Laboratory of Physical Chemistry, Wolfgang-Pauli-Str. 10. CH-8093 Zurich, Switzerland.
| | | | | |
Collapse
|
23
|
Gould AD, Telmer PG, Shilton BH. Stimulation of the maltose transporter ATPase by unliganded maltose binding protein. Biochemistry 2009; 48:8051-61. [PMID: 19630440 PMCID: PMC2809251 DOI: 10.1021/bi9007066] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ATP hydrolysis by the maltose transporter (MalFGK(2)) is regulated by maltose binding protein (MBP). Binding of maltose to MBP brings about a conformational change from open to closed that leads to a strong stimulation of the MalFGK(2) ATPase. In this study, we address the long-standing but enigmatic observation that unliganded MBP is also able to stimulate MalFGK(2). Although the mechanism of this stimulation is not understood, it is sometimes attributed to a small amount of closed (but unliganded) MBP that may exist in solution. To gain insight into how MBP regulates the MalFGK(2) ATPase, we have investigated whether the open or the closed conformation of MBP is responsible for MalFGK(2) stimulation in the absence of maltose. The effect of MBP concentration on the stimulation of MalFGK(2) was assessed: for unliganded MBP, the apparent K(M) for stimulation of MalFGK(2) was below 1 microM, while for maltose-bound MBP, the K(M) was approximately 15 microM. We show that engineered MBP molecules in which the open-closed equilibrium has been shifted toward the closed conformation have a decreased ability to stimulate MalFGK(2). These results indicate that stimulation of the MalFGK(2) ATPase by unliganded MBP does not proceed through a closed conformation and instead must operate through a different mechanism than stimulation by liganded MBP. One possible explanation is that the open conformation is able to activate the MalFGK(2) ATPase directly.
Collapse
Affiliation(s)
| | | | - Brian H. Shilton
- Department of Biochemistry, The University of Western Ontario, 1151 Richmond St., London, Ontario Canada N6A 5C1
| |
Collapse
|
24
|
Abstract
AbstractIn order to fulfill their function, membrane transport proteins have to cycle through a number of conformational and/or energetic states. Thus, understanding the role of conformational dynamics seems to be the key for elucidation of the functional mechanism of these proteins. However, membrane proteins in general are often difficult to express heterologously and in sufficient amounts for structural studies. It is especially challenging to trap a stable energy minimum, e.g., for crystallographic analysis. Furthermore, crystallization is often only possible by subjecting the protein to conditions that do not resemble its native environment and crystals can only be snapshots of selected conformational states. Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy are complementary methods that offer unique possibilities for studying membrane proteins in their natural membrane environment and for investigating functional conformational changes, lipid interactions, substrate-lipid and substrate-protein interactions, oligomerization states and overall dynamics of membrane transporters. Here, we review recent progress in the field including studies from primary and secondary active transporters.
Collapse
|
25
|
Grote M, Polyhach Y, Jeschke G, Steinhoff HJ, Schneider E, Bordignon E. Transmembrane signaling in the maltose ABC transporter MalFGK2-E: periplasmic MalF-P2 loop communicates substrate availability to the ATP-bound MalK dimer. J Biol Chem 2009; 284:17521-6. [PMID: 19395376 DOI: 10.1074/jbc.m109.006270] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ABC transporters are ubiquitous membrane proteins that translocate solutes across biological membranes at the expense of ATP. In prokaryotic ABC importers, the extracytoplasmic anchoring of the substrate-binding protein (receptor) is emerging as a key determinant for the structural rearrangements in the cytoplasmically exposed ATP-binding cassette domains and in the transmembrane gates during the nucleotide cycle. Here the molecular mechanism of such signaling events was addressed by electron paramagnetic resonance spectroscopy of spin-labeled ATP-binding cassette maltose transporter variants (MalFGK2-E). A series of doubly spin-labeled mutants in the MalF-P2 domain involving positions 92, 205, 239, 252, and 273 and one triple mutant labeled at positions 205/252 in P2 and 83 in the Q-loop of MalK were assayed. The EPR data revealed that the substrate-binding protein MalE is bound to the transporter throughout the transport cycle. Concomitantly with the three conformations of the ATP-binding cassette MalK2, three functionally relevant conformations are found also in the periplasmic MalF-P2 loop, strictly dependent on cytoplasmic nucleotide binding and periplasmic docking of liganded MalE to MalFG. The reciprocal communication across the membrane unveiled here gives first insights into the stimulatory effect of MalE on the ATPase activity, and it is suggested to be an important mechanistic feature of receptor-coupled ABC transporters.
Collapse
Affiliation(s)
- Mathias Grote
- Institut für Biologie/Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany
| | | | | | | | | | | |
Collapse
|