1
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Sikorskaya TV, Ermolenko EV, Ginanova TT, Boroda AV, Efimova KV, Bogdanov M. Membrane vectorial lipidomic features of coral host cells' plasma membrane and lipid profiles of their endosymbionts Cladocopium. Commun Biol 2024; 7:878. [PMID: 39025984 PMCID: PMC11258240 DOI: 10.1038/s42003-024-06578-8] [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: 01/14/2024] [Accepted: 07/11/2024] [Indexed: 07/20/2024] Open
Abstract
The symbiotic relationships between coral animal host and autotrophic dinoflagellates are based on the mutual exchange and tight control of nutritional inputs supporting successful growth. The corals Sinularia heterospiculata and Acropora aspera were cultivated using a flow-through circulation system supplying seawater during cold and warm seasons of the year, then sorted into host cells and symbionts and subjected to phylogenetic, morphological, and advanced lipid analyses. Here we show, that the lipidomes of the dinoflagellates Cladocopium C1/C3 and acroporide-specific Cladocopium hosted by the corals, are determined by lipidomic features of different thermosensitivity and unique betaine- and phospholipid molecular species. Phosphatidylserines and ceramiaminoethylphosphonates are not detected in the symbionts and predominantly localized on the inner leaflet of the S. heterospiculata host plasma membrane. The transmembrane distribution of phosphatidylethanolamines of S. heterospiculata host changes during different seasons of the year, possibly contributing to mutualistic nutritional exchange across this membrane complex to provide the host with a secure adaptive mechanism and ecological benefits.
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Affiliation(s)
- Tatyana V Sikorskaya
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russian Federation.
| | - Ekaterina V Ermolenko
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russian Federation
| | - Taliya T Ginanova
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russian Federation
| | - Andrey V Boroda
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russian Federation
| | - Kseniya V Efimova
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russian Federation
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, the University of Texas Health Science Center, McGovern Medical School, Houston, TX, USA.
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2
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Kwarteng DO, Gangoda M, Kooijman EE. The effect of methylated phosphatidylethanolamine derivatives on the ionization properties of signaling phosphatidic acid. Biophys Chem 2023; 296:107005. [PMID: 36934676 DOI: 10.1016/j.bpc.2023.107005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 03/07/2023] [Indexed: 03/16/2023]
Abstract
Phosphatidylethanolamine (PE) and Phosphatidylcholine (PC) are the most abundant glycerophospholipids in eukaryotic membranes. The differences in the physicochemical properties of their headgroups have contrasting modulatory effects on their interaction with intracellular macromolecules. As such, their overall impact on membrane structure and function differs significantly. Enzymatic methylation of PE's amine headgroup produces two methylated derivatives namely monomethyl PE (MMPE) and dimethyl PE (DMPE) which have physicochemical properties that generally range between that of PE and PC. Additionally, their influence on membrane properties differs from both PE and PC. Although variations in headgroup methylation have been reported to affect signaling pathways, the direct influence that these differences exert on the ionization properties of signaling phospholipids have not been investigated. Here, we briefly review membrane function and structure that are mediated by the differences in headgroup methylation between PE, MMPE, DMPE and PC. In addition, using 31P MAS NMR, we investigate the effect of these four phospholipids on the ionization properties of the ubiquitous signaling anionic lipid phosphatidic acid (PA). Our results show that PA's ionization properties are differentially affected by changes in phospholipid headgroup methylation. This could have important implications for PA-protein binding and hence physiological functions in cells where signaling events lead to changes in abundance of methylated PE derivatives in the membrane.
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Affiliation(s)
- Desmond Owusu Kwarteng
- Department of Biological Sciences, Kent State University, P.O. Box 5190, Kent, OH 44242, USA.
| | - Mahinda Gangoda
- Department of Chemistry & Biochemistry, Kent State University, P.O. Box 5190, Kent, OH 44242, USA
| | - Edgar E Kooijman
- Department of Biological Sciences, Kent State University, P.O. Box 5190, Kent, OH 44242, USA.
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3
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Chen I, Wu Q, Font J, Ryan RM. The twisting elevator mechanism of glutamate transporters reveals the structural basis for the dual transport-channel functions. Curr Opin Struct Biol 2022; 75:102405. [PMID: 35709614 DOI: 10.1016/j.sbi.2022.102405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/10/2022] [Accepted: 05/12/2022] [Indexed: 11/16/2022]
Abstract
Glutamate transporters facilitate the removal of this excitatory neurotransmitter from the synapse. Increasing evidence indicates that this process is linked to intrinsic chloride channel activity that is thermodynamically uncoupled from substrate transport. A recent cryo-EM structure of GltPh - an archaeal homolog of the glutamate transporters - in an open channel state has shed light on the structural basis for channel opening formed at the interface of two domains within the transporter which is gated by two clusters of hydrophobic residues. These transporters cycle through several conformational states during the transport process, including the chloride conducting state, which appears to be stabilised by protein-membrane interactions and membrane deformation. Several point mutations that perturb the chloride conductance can have detrimental effects and are linked to the pathogenesis of the neurological disorder, episodic ataxia type 6.
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Affiliation(s)
- Ichia Chen
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Qianyi Wu
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Josep Font
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia.
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4
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Corin K, Bowie JU. How physical forces drive the process of helical membrane protein folding. EMBO Rep 2022; 23:e53025. [PMID: 35133709 PMCID: PMC8892262 DOI: 10.15252/embr.202153025] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/17/2021] [Accepted: 11/24/2021] [Indexed: 11/09/2022] Open
Abstract
Protein folding is a fundamental process of life with important implications throughout biology. Indeed, tens of thousands of mutations have been associated with diseases, and most of these mutations are believed to affect protein folding rather than function. Correct folding is also a key element of design. These factors have motivated decades of research on protein folding. Unfortunately, knowledge of membrane protein folding lags that of soluble proteins. This gap is partly caused by the greater technical challenges associated with membrane protein studies, but also because of additional complexities. While soluble proteins fold in a homogenous water environment, membrane proteins fold in a setting that ranges from bulk water to highly charged to apolar. Thus, the forces that drive folding vary in different regions of the protein, and this complexity needs to be incorporated into our understanding of the folding process. Here, we review our understanding of membrane protein folding biophysics. Despite the greater challenge, better model systems and new experimental techniques are starting to unravel the forces and pathways in membrane protein folding.
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Affiliation(s)
- Karolina Corin
- Department of Chemistry and BiochemistryMolecular Biology InstituteUCLA‐DOE InstituteUniversity of CaliforniaLos AngelesCAUSA
| | - James U Bowie
- Department of Chemistry and BiochemistryMolecular Biology InstituteUCLA‐DOE InstituteUniversity of CaliforniaLos AngelesCAUSA
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5
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Danbolt NC, López-Corcuera B, Zhou Y. Reconstitution of GABA, Glycine and Glutamate Transporters. Neurochem Res 2022; 47:85-110. [PMID: 33905037 PMCID: PMC8763731 DOI: 10.1007/s11064-021-03331-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 04/13/2021] [Accepted: 04/15/2021] [Indexed: 10/25/2022]
Abstract
In contrast to water soluble enzymes which can be purified and studied while in solution, studies of solute carrier (transporter) proteins require both that the protein of interest is situated in a phospholipid membrane and that this membrane forms a closed compartment. An additional challenge to the study of transporter proteins has been that the transport depends on the transmembrane electrochemical gradients. Baruch I. Kanner understood this early on and first developed techniques for studying plasma membrane vesicles. This advanced the field in that the experimenter could control the electrochemical gradients. Kanner, however, did not stop there, but started to solubilize the membranes so that the transporter proteins were taken out of their natural environment. In order to study them, Kanner then had to find a way to reconstitute them (reinsert them into phospholipid membranes). The scope of the present review is both to describe the reconstitution method in full detail as that has never been done, and also to reveal the scientific impact that this method has had. Kanner's later work is not reviewed here although that also deserves a review because it too has had a huge impact.
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Affiliation(s)
- Niels Christian Danbolt
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317, Oslo, Norway.
| | - Beatriz López-Corcuera
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Biología Molecular "Severo Ochoa" Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
- IdiPAZ, Hospital Universitario La Paz, Madrid, Spain
| | - Yun Zhou
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317, Oslo, Norway
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6
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Do HQ, Bassil CM, Andersen EI, Jansen M. Impact of nanodisc lipid composition on cell-free expression of proton-coupled folate transporter. PLoS One 2021; 16:e0253184. [PMID: 34793461 PMCID: PMC8601550 DOI: 10.1371/journal.pone.0253184] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 10/31/2021] [Indexed: 01/19/2023] Open
Abstract
The Proton-Coupled Folate Transporter (PCFT) is a transmembrane transport protein that controls the absorption of dietary folates in the small intestine. PCFT also mediates uptake of chemotherapeutically used antifolates into tumor cells. PCFT has been identified within lipid rafts observed in phospholipid bilayers of plasma membranes, a micro environment that is altered in tumor cells. The present study aimed at investigating the impact of different lipids within Lipid-protein nanodiscs (LPNs), discoidal lipid structures stabilized by membrane scaffold proteins, to yield soluble PCFT expression in an E. coli lysate-based cell-free transcription/translation system. In the absence of detergents or lipids, we observed PCFT quantitatively as precipitate in this system. We then explored the ability of LPNs to support solubilized PCFT expression when present during in-vitro translation. LPNs consisted of either dimyristoyl phosphatidylcholine (DMPC), palmitoyl-oleoyl phosphatidylcholine (POPC), or dimyristoyl phosphatidylglycerol (DMPG). While POPC did not lead to soluble PCFT expression, both DMPG and DMPC supported PCFT translation directly into LPNs, the latter in a concentration dependent manner. The results obtained through this study provide insights into the lipid preferences of PCFT. Membrane-embedded or solubilized PCFT will enable further studies with diverse biophysical approaches to enhance the understanding of the structure and molecular mechanism of folate transport through PCFT.
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Affiliation(s)
- Hoa Quynh Do
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Carla M. Bassil
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
- The Clark Scholar Program, Texas Tech University, Lubbock, TX, United States of America
| | - Elizabeth I. Andersen
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Michaela Jansen
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
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7
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Elucidating the Mechanism Behind Sodium-Coupled Neurotransmitter Transporters by Reconstitution. Neurochem Res 2021; 47:127-137. [PMID: 34347265 DOI: 10.1007/s11064-021-03413-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 07/01/2021] [Accepted: 07/27/2021] [Indexed: 10/20/2022]
Abstract
Sodium-coupled neurotransmitter transporters play a fundamental role in the termination of synaptic neurotransmission, which makes them a major drug target. The reconstitution of these secondary active transporters into liposomes has shed light on their molecular transport mechanisms. From the earliest days of the reconstitution technique up to today's single-molecule studies, insights from live functioning transporters have been indispensable for our understanding of their physiological impact. The two classes of sodium-coupled neurotransmitter transporters, the neurotransmitter: sodium symporters and the excitatory amino acid transporters, have vastly different molecular structures, but complementary proteoliposome studies have sought to unravel their ion-dependence and transport kinetics. Furthermore, reconstitution experiments have been used on both protein classes to investigate the role of e.g. the lipid environment, of posttranslational modifications, and of specific amino acid residues in transport. Techniques that allow the detection of transport at a single-vesicle resolution have been developed, and single-molecule studies have started to reveal single transporter kinetics, which will expand our understanding of how transport across the membrane is facilitated at protein level. Here, we review a selection of the results and applications where the reconstitution of the two classes of neurotransmitter transporters has been instrumental.
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8
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Dowhan W, Bogdanov M. Eugene P. Kennedy's Legacy: Defining Bacterial Phospholipid Pathways and Function. Front Mol Biosci 2021; 8:666203. [PMID: 33842554 PMCID: PMC8027125 DOI: 10.3389/fmolb.2021.666203] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 03/01/2021] [Indexed: 12/27/2022] Open
Abstract
In the 1950's and 1960's Eugene P. Kennedy laid out the blueprint for phospholipid biosynthesis in somatic cells and Escherichia coli, which have been coined the Kennedy Pathways for phospholipid biosynthesis. His research group continued to make seminal contributions in the area of phospholipids until his retirement in the early 1990's. During these years he mentored many young scientists that continued to build on his early discoveries and who also mentored additional scientists that continue to make important contributions in areas related to phospholipids and membrane biogenesis. This review will focus on the initial E. coli Kennedy Pathways and how his early contributions have laid the foundation for our current understanding of bacterial phospholipid genetics, biochemistry and function as carried on by his scientific progeny and others who have been inspired to study microbial phospholipids.
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Affiliation(s)
- William Dowhan
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, United States
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, United States
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9
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Fortea E, Accardi A. A quantitative flux assay for the study of reconstituted Cl - channels and transporters. Methods Enzymol 2021; 652:243-272. [PMID: 34059284 DOI: 10.1016/bs.mie.2021.01.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The recent deluge of high-resolution structural information on membrane proteins has not been accompanied by a comparable increase in our ability to functionally interrogate these proteins. Current functional assays often are not quantitative or are performed in conditions that significantly differ from those used in structural experiments, thus limiting the mechanistic correspondence between structural and functional experiments. A flux assay to determine quantitatively the functional properties of purified and reconstituted Cl- channels and transporters in membranes of defined lipid compositions is described. An ion-sensitive electrode is used to measure the rate of Cl- efflux from proteoliposomes reconstituted with the desired protein and the fraction of vesicles containing at least one active protein. These measurements enable the quantitative determination of key molecular parameters such as the unitary transport rate, the fraction of proteins that are active, and the molecular mass of the transport protein complex. The approach is illustrated using CLC-ec1, a CLC-type H+/Cl- exchanger as an example. The assay enables the quantitative study of a wide range of Cl- transporting molecules and proteins whose activity is modulated by ligands, voltage, and membrane composition as well as the investigation of the effects of compounds that directly inhibit or activate the reconstituted transport systems. The present assay is readily adapted to the study of transport systems with diverse substrate specificities and molecular characteristics, and the necessary modifications needed are discussed.
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Affiliation(s)
- Eva Fortea
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, United States
| | - Alessio Accardi
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, United States; Department of Anesthesiology, Weill Cornell Medical College, New York, NY, United States; Department of Biochemistry, Weill Cornell Medical College, New York, NY, United States.
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10
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Elevator-type mechanisms of membrane transport. Biochem Soc Trans 2021; 48:1227-1241. [PMID: 32369548 PMCID: PMC7329351 DOI: 10.1042/bst20200290] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 03/29/2020] [Accepted: 03/31/2020] [Indexed: 12/13/2022]
Abstract
Membrane transporters are integral membrane proteins that mediate the passage of solutes across lipid bilayers. These proteins undergo conformational transitions between outward- and inward-facing states, which lead to alternating access of the substrate-binding site to the aqueous environment on either side of the membrane. Dozens of different transporter families have evolved, providing a wide variety of structural solutions to achieve alternating access. A sub-set of structurally diverse transporters operate by mechanisms that are collectively named 'elevator-type'. These transporters have one common characteristic: they contain a distinct protein domain that slides across the membrane as a rigid body, and in doing so it 'drags" the transported substrate along. Analysis of the global conformational changes that take place in membrane transporters using elevator-type mechanisms reveals that elevator-type movements can be achieved in more than one way. Molecular dynamics simulations and experimental data help to understand how lipid bilayer properties may affect elevator movements and vice versa.
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11
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Corin K, Bowie JU. How bilayer properties influence membrane protein folding. Protein Sci 2020; 29:2348-2362. [PMID: 33058341 DOI: 10.1002/pro.3973] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/07/2020] [Accepted: 10/09/2020] [Indexed: 01/24/2023]
Abstract
The question of how proteins manage to organize into a unique three-dimensional structure has been a major field of study since the first protein structures were determined. For membrane proteins, the question is made more complex because, unlike water-soluble proteins, the solvent is not homogenous or even unique. Each cell and organelle has a distinct lipid composition that can change in response to environmental stimuli. Thus, the study of membrane protein folding requires not only understanding how the unfolded chain navigates its way to the folded state, but also how changes in bilayer properties can affect that search. Here we review what we know so far about the impact of lipid composition on bilayer physical properties and how those properties can affect folding. A better understanding of the lipid bilayer and its effects on membrane protein folding is not only important for a theoretical understanding of the folding process, but can also have a practical impact on our ability to work with and design membrane proteins.
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Affiliation(s)
- Karolina Corin
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA-DOE Institute, University of California, Los Angeles, California, USA
| | - James U Bowie
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA-DOE Institute, University of California, Los Angeles, California, USA
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12
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Matin TR, Heath GR, Huysmans GHM, Boudker O, Scheuring S. Millisecond dynamics of an unlabeled amino acid transporter. Nat Commun 2020; 11:5016. [PMID: 33024106 PMCID: PMC7538599 DOI: 10.1038/s41467-020-18811-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 09/16/2020] [Indexed: 12/14/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) are important in many physiological processes and crucial for the removal of excitatory amino acids from the synaptic cleft. Here, we develop and apply high-speed atomic force microscopy line-scanning (HS-AFM-LS) combined with automated state assignment and transition analysis for the determination of transport dynamics of unlabeled membrane-reconstituted GltPh, a prokaryotic EAAT homologue, with millisecond temporal resolution. We find that GltPh transporters can operate much faster than previously reported, with state dwell-times in the 50 ms range, and report the kinetics of an intermediate transport state with height between the outward- and inward-facing states. Transport domains stochastically probe transmembrane motion, and reversible unsuccessful excursions to the intermediate state occur. The presented approach and analysis methodology are generally applicable to study transporter kinetics at system-relevant temporal resolution. Excitatory amino acid transporters (EAATs) are crucial for the removal of excitatory amino acids from the synaptic cleft. Here authors combined high-speed atomic force microscopy line-scanning with automated state assignment for the determination of transport dynamics of GltPh, a prokaryotic EAAT homologue, with millisecond temporal resolution.
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Affiliation(s)
- Tina R Matin
- Department of Anesthesiology, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA.,Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA
| | - George R Heath
- Department of Anesthesiology, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA.,Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA
| | - Gerard H M Huysmans
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA.,Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Simon Scheuring
- Department of Anesthesiology, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA. .,Department of Physiology and Biophysics, Weill Cornell Medicine, 1300 York Avenue, New York, NY, 10065, USA.
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13
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Target the human Alanine/Serine/Cysteine Transporter 2(ASCT2): Achievement and Future for Novel Cancer Therapy. Pharmacol Res 2020; 158:104844. [DOI: 10.1016/j.phrs.2020.104844] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 04/12/2020] [Accepted: 04/13/2020] [Indexed: 12/11/2022]
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14
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Arkhipova V, Guskov A, Slotboom DJ. Structural ensemble of a glutamate transporter homologue in lipid nanodisc environment. Nat Commun 2020; 11:998. [PMID: 32081874 PMCID: PMC7035293 DOI: 10.1038/s41467-020-14834-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 02/04/2020] [Indexed: 12/19/2022] Open
Abstract
Glutamate transporters are cation-coupled secondary active membrane transporters that clear the neurotransmitter L-glutamate from the synaptic cleft. These transporters are homotrimers, with each protomer functioning independently by an elevator-type mechanism, in which a mobile transport domain alternates between inward- and outward-oriented states. Using single-particle cryo-EM we have determined five structures of the glutamate transporter homologue GltTk, a Na+- L-aspartate symporter, embedded in lipid nanodiscs. Dependent on the substrate concentrations used, the protomers of the trimer adopt a variety of asymmetrical conformations, consistent with the independent movement. Six of the 15 resolved protomers are in a hitherto elusive state of the transport cycle in which the inward-facing transporters are loaded with Na+ ions. These structures explain how substrate-leakage is prevented - a strict requirement for coupled transport. The belt protein of the lipid nanodiscs bends around the inward oriented protomers, suggesting that membrane deformations occur during transport.
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Affiliation(s)
- Valentina Arkhipova
- Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands
| | - Albert Guskov
- Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands. .,Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
| | - Dirk J Slotboom
- Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands. .,Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG, Groningen, The Netherlands.
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15
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Abstract
Due to the heterogenous lipid environment in which integral membrane proteins are embedded, they should follow a set of assembly rules, which govern transmembrane protein folding and topogenesis accordingly to a given lipid profile. Recombinant strains of bacteria have been engineered to have different membrane phospholipid compositions by molecular genetic manipulation of endogenous and foreign genes encoding lipid biosynthetic enzymes. Such strains provide a means to investigate the in vivo role of lipids in many different aspects of membrane function, folding and biogenesis. In vitro and in vivo studies established a function of lipids as molecular chaperones and topological determinants specifically assisting folding and topogenesis of membrane proteins. These results led to the extension of the Positive Inside Rule to Charge Balance Rule, which incorporates a role for lipid-protein interactions in determining membrane protein topological organization at the time of initial membrane insertion and dynamically after initial assembly. Membrane protein topogenesis appears to be a thermodynamically driven process in which lipid-protein interactions affect the potency of charged amino acid residues as topological signals. Dual topology for a membrane protein can be established during initial assembly where folding intermediates in multiple topological conformations are in rapid equilibrium (thus separated by a low activation energy), which is determined by the lipid environment. Post-assembly changes in lipid composition or post-translational modifications can trigger a reorganization of protein topology by inducing destabilization and refolding of a membrane protein. The lipid-dependent dynamic nature of membrane protein organization provides a novel means of regulating protein function.
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16
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Wang X, Boudker O. Large domain movements through the lipid bilayer mediate substrate release and inhibition of glutamate transporters. eLife 2020; 9:58417. [PMID: 33155546 PMCID: PMC7682989 DOI: 10.7554/elife.58417] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 11/05/2020] [Indexed: 01/21/2023] Open
Abstract
Glutamate transporters are essential players in glutamatergic neurotransmission in the brain, where they maintain extracellular glutamate below cytotoxic levels and allow for rounds of transmission. The structural bases of their function are well established, particularly within a model archaeal homolog, sodium, and aspartate symporter GltPh. However, the mechanism of gating on the cytoplasmic side of the membrane remains ambiguous. We report Cryo-EM structures of GltPh reconstituted into nanodiscs, including those structurally constrained in the cytoplasm-facing state and either apo, bound to sodium ions only, substrate, or blockers. The structures show that both substrate translocation and release involve movements of the bulky transport domain through the lipid bilayer. They further reveal a novel mode of inhibitor binding and show how solutes release is coupled to protein conformational changes. Finally, we describe how domain movements are associated with the displacement of bound lipids and significant membrane deformations, highlighting the potential regulatory role of the bilayer.
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Affiliation(s)
- Xiaoyu Wang
- Department of Physiology and Biophysics, Weill Cornell MedicineNew YorkUnited States
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell MedicineNew YorkUnited States,Howard Hughes Medical InstituteChevy ChaseUnited States
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17
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Zhou W, Fiorin G, Anselmi C, Karimi-Varzaneh HA, Poblete H, Forrest LR, Faraldo-Gómez JD. Large-scale state-dependent membrane remodeling by a transporter protein. eLife 2019; 8:50576. [PMID: 31855177 PMCID: PMC6957315 DOI: 10.7554/elife.50576] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 12/17/2019] [Indexed: 12/22/2022] Open
Abstract
That channels and transporters can influence the membrane morphology is increasingly recognized. Less appreciated is that the extent and free-energy cost of these deformations likely varies among different functional states of a protein, and thus, that they might contribute significantly to defining its mechanism. We consider the trimeric Na+-aspartate symporter GltPh, a homolog of an important class of neurotransmitter transporters, whose mechanism entails one of the most drastic structural changes known. Molecular simulations indicate that when the protomers become inward-facing, they cause deep, long-ranged, and yet mutually-independent membrane deformations. Using a novel simulation methodology, we estimate that the free-energy cost of this membrane perturbation is in the order of 6–7 kcal/mol per protomer. Compensating free-energy contributions within the protein or its environment must thus stabilize this inward-facing conformation for the transporter to function. We discuss these striking results in the context of existing experimental observations for this and other transporters.
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Affiliation(s)
- Wenchang Zhou
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Giacomo Fiorin
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Claudio Anselmi
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Hossein Ali Karimi-Varzaneh
- Computational Structural Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Horacio Poblete
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States.,Computational Structural Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Lucy R Forrest
- Computational Structural Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - José D Faraldo-Gómez
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
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18
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A Perspective: Active Role of Lipids in Neurotransmitter Dynamics. Mol Neurobiol 2019; 57:910-925. [PMID: 31595461 PMCID: PMC7031182 DOI: 10.1007/s12035-019-01775-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 09/01/2019] [Indexed: 12/30/2022]
Abstract
Synaptic neurotransmission is generally considered as a function of membrane-embedded receptors and ion channels in response to the neurotransmitter (NT) release and binding. This perspective aims to widen the protein-centric view by including another vital component—the synaptic membrane—in the discussion. A vast set of atomistic molecular dynamics simulations and biophysical experiments indicate that NTs are divided into membrane-binding and membrane-nonbinding categories. The binary choice takes place at the water-membrane interface and follows closely the positioning of the receptors’ binding sites in relation to the membrane. Accordingly, when a lipophilic NT is on route to a membrane-buried binding site, it adheres on the membrane and, then, travels along its plane towards the receptor. In contrast, lipophobic NTs, which are destined to bind into receptors with extracellular binding sites, prefer the water phase. This membrane-based sorting splits the neurotransmission into membrane-independent and membrane-dependent mechanisms and should make the NT binding into the receptors more efficient than random diffusion would allow. The potential implications and notable exceptions to the mechanisms are discussed here. Importantly, maintaining specific membrane lipid compositions (MLCs) at the synapses, especially regarding anionic lipids, affect the level of NT-membrane association. These effects provide a plausible link between the MLC imbalances and neurological diseases such as depression or Parkinson’s disease. Moreover, the membrane plays a vital role in other phases of the NT life cycle, including storage and release from the synaptic vesicles, transport from the synaptic cleft, as well as their synthesis and degradation.
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19
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Chen E, Kiebish MA, McDaniel J, Niedzwiecka K, Kucharczyk R, Ravasz D, Gao F, Narain NR, Sarangarajan R, Seyfried TN, Adam-Vizi V, Chinopoulos C. Perturbation of the yeast mitochondrial lipidome and associated membrane proteins following heterologous expression of Artemia-ANT. Sci Rep 2018; 8:5915. [PMID: 29651047 PMCID: PMC5897331 DOI: 10.1038/s41598-018-24305-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/29/2018] [Indexed: 12/22/2022] Open
Abstract
Heterologous expression is a landmark technique for studying a protein itself or its effect on the expression host, in which membrane-embedded proteins are a common choice. Yet, the impact of inserting a foreign protein to the lipid environment of host membranes, has never been addressed. Here we demonstrated that heterologous expression of the Artemia franciscana adenine nucleotide translocase (ANT) in yeasts altered lipidomic composition of their inner mitochondrial membranes. Along with this, activities of complex II, IV and ATP synthase, all membrane-embedded components, were significantly decreased while their expression levels remained unaffected. Although the results represent an individual case of expressing a crustacean protein in yeast inner mitochondrial membranes, it cannot be excluded that host lipidome alterations is a more widespread epiphenomenon, potentially biasing heterologous expression experiments. Finally, our results raise the possibility that not only lipids modulate protein function, but also membrane-embedded proteins modulate lipid composition, thus revealing a reciprocal mode of regulation for these two biomolecular entities.
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Affiliation(s)
| | | | | | - Katarzyna Niedzwiecka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02-106, Poland
| | - Roza Kucharczyk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02-106, Poland
| | - Dora Ravasz
- Department of Medical Biochemistry, Semmelweis University, Budapest, 1094, Hungary.,MTA-SE Lendület Neurobiochemistry Research Group, Budapest, 1094, Hungary
| | - Fei Gao
- BERG LLC, Framingham, MA, 01701, USA
| | | | | | - Thomas N Seyfried
- Biology Department, Boston College, Chestnut Hill, Boston, MA, 02467, USA
| | - Vera Adam-Vizi
- Department of Medical Biochemistry, Semmelweis University, Budapest, 1094, Hungary.,MTA-SE Laboratory for Neurobiochemistry, Budapest, 1094, Hungary
| | - Christos Chinopoulos
- Department of Medical Biochemistry, Semmelweis University, Budapest, 1094, Hungary. .,MTA-SE Lendület Neurobiochemistry Research Group, Budapest, 1094, Hungary.
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20
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Effects of Ca2+, Glu and GABA on hBest1 and composite hBest1/POPC surface films. Colloids Surf B Biointerfaces 2018; 161:192-199. [DOI: 10.1016/j.colsurfb.2017.10.051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 10/11/2017] [Accepted: 10/17/2017] [Indexed: 12/22/2022]
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21
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Ren T, Erbakan M, Shen Y, Barbieri E, Saboe P, Feroz H, Yan H, McCuskey S, Hall JF, Schantz AB, Bazan GC, Butler PJ, Grzelakowski M, Kumar M. Membrane Protein Insertion into and Compatibility with Biomimetic Membranes. ACTA ACUST UNITED AC 2017; 1:e1700053. [DOI: 10.1002/adbi.201700053] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 05/07/2017] [Indexed: 11/12/2022]
Affiliation(s)
- Tingwei Ren
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
| | - Mustafa Erbakan
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
- Department of Biosystem Engineering Bozok University Yozgat 66000 Turkey
| | - Yuexiao Shen
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
| | - Eduardo Barbieri
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
- Departamento de Engenharia Química Universidade Federal do Rio de Janeiro Centro de Tecnologia Bloco E Rio de Janeiro RJ CEP 21941‐909 Brazil
| | - Patrick Saboe
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
| | - Hasin Feroz
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
| | - Hengjing Yan
- Department of Chemistry and Biochemistry University of California Santa Barbara CA 93106 USA
| | - Samantha McCuskey
- Department of Chemistry and Biochemistry University of California Santa Barbara CA 93106 USA
| | - Joseph F. Hall
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
| | - A. Benjamin Schantz
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
| | - Guillermo C. Bazan
- Department of Chemistry and Biochemistry University of California Santa Barbara CA 93106 USA
| | - Peter J. Butler
- Department of Biomedical Engineering The Pennsylvania State University University Park PA USA 16802
| | | | - Manish Kumar
- Department of Chemical Engineering The Pennsylvania State University University Park PA 16802 USA
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22
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Vitrac H, Dowhan W, Bogdanov M. Effects of mixed proximal and distal topogenic signals on the topological sensitivity of a membrane protein to the lipid environment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1291-1300. [PMID: 28432030 DOI: 10.1016/j.bbamem.2017.04.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 03/27/2017] [Accepted: 04/12/2017] [Indexed: 10/19/2022]
Abstract
The final topology of membrane proteins is thought to be dictated primarily by the encoding sequence. However, according to the Charge Balance Rule the topogenic signals within nascent membrane proteins are interpreted in agreement with the Positive Inside Rule as influenced by the protein phospholipid environment. The role of long-range protein-lipid interactions in establishing a final uniform or dual topology is unknown. In order to address this role, we determined the positional dependence of the potency of charged residues as topological signals within Escherichia coli sucrose permease (CscB) in cells in which the zwitterionic phospholipid phosphatidylethanolamine (PE), acting as topological determinant, was either eliminated or tightly titrated. Although the position of a single or paired oppositely charged amino acid residues within an extramembrane domain (EMD), either proximal, central or distal to a transmembrane domain (TMD) end, does not appear to be important, the oppositely charged residues exert their topogenic effects separately only in the absence of PE. Thus, the Charge Balance Rule can be executed in a retrograde manner from any cytoplasmic EMD or any residue within an EMD most likely outside of the translocon. Moreover, CscB is inserted into the membrane in two opposite orientations at different ratios with the native orientation proportional to the mol % of PE. The results demonstrate how the cooperative contribution of lipid-protein interactions affects the potency of charged residues as topological signals, providing a molecular mechanism for the realization of single, equal or different amounts of oppositely oriented protein within the same membrane.
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Affiliation(s)
- Heidi Vitrac
- Department of Biochemistry and Molecular Biology, the University of Texas Health Science Center McGovern Medical School, Houston, TX 77030, USA
| | - William Dowhan
- Department of Biochemistry and Molecular Biology, the University of Texas Health Science Center McGovern Medical School, Houston, TX 77030, USA
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, the University of Texas Health Science Center McGovern Medical School, Houston, TX 77030, USA.
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23
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Canul-Tec JC, Assal R, Cirri E, Legrand P, Brier S, Chamot-Rooke J, Reyes N. Structure and allosteric inhibition of excitatory amino acid transporter 1. Nature 2017; 544:446-451. [PMID: 28424515 PMCID: PMC5410168 DOI: 10.1038/nature22064] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 03/10/2017] [Indexed: 12/24/2022]
Abstract
Human members of the solute carrier 1 (SLC1) family of transporters take up excitatory neurotransmitters in the brain and amino acids in peripheral organs. Dysregulation of the function of SLC1 transporters is associated with neurodegenerative disorders and cancer. Here we present crystal structures of a thermostabilized human SLC1 transporter, the excitatory amino acid transporter 1 (EAAT1), with and without allosteric and competitive inhibitors bound. The structures reveal architectural features of the human transporters, such as intra- and extracellular domains that have potential roles in transport function, regulation by lipids and post-translational modifications. The coordination of the allosteric inhibitor in the structures and the change in the transporter dynamics measured by hydrogen-deuterium exchange mass spectrometry reveal a mechanism of inhibition, in which the transporter is locked in the outward-facing states of the transport cycle. Our results provide insights into the molecular mechanisms underlying the function and pharmacology of human SLC1 transporters.
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Affiliation(s)
- Juan C Canul-Tec
- Molecular Mechanisms of Membrane Transport Laboratory, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.,UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France
| | - Reda Assal
- Molecular Mechanisms of Membrane Transport Laboratory, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.,UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France
| | - Erica Cirri
- Molecular Mechanisms of Membrane Transport Laboratory, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.,UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France
| | - Pierre Legrand
- Synchrotron SOLEIL, L'Orme des Merisiers, 91192 Gif-sur-Yvette, France
| | - Sébastien Brier
- Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.,UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France
| | - Julia Chamot-Rooke
- Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.,UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France
| | - Nicolas Reyes
- Molecular Mechanisms of Membrane Transport Laboratory, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.,UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France
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24
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McIlwain BC, Vandenberg RJ, Ryan RM. Characterization of the Inward- and Outward-Facing Substrate Binding Sites of the Prokaryotic Aspartate Transporter, Glt Ph. Biochemistry 2016; 55:6801-6810. [PMID: 27951659 DOI: 10.1021/acs.biochem.6b00795] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Crystal structures of the prokaryotic aspartate transporter, GltPh, have provided important insights into the mechanism of amino acid transport by GltPh and related eukaryotic members of the glutamate transporter family (SLC1A family). Identification of inhibitors of GltPh can provide valuable tools for understanding the molecular basis for substrate and inhibitor specificity and selectivity of SLC1A members, but at present, few inhibitors of GltPh have been identified. We have screened a collection of commercially available aspartate analogues and identified new transportable and nontransportable GltPh inhibitors. We have explored the inhibition profile of GltPh by utilizing a thiol modification assay that isolates sided populations of the transporters reconstituted in liposomes to determine if any aspartate analogues display a preference for either the inwardly or outwardly directed binding sites. Here, we have characterized several new inhibitors of GltPh and identified three β-carbon-substituted molecules that display a strong preference for the outwardly directed binding site of GltPh.
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Affiliation(s)
- Benjamin C McIlwain
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney , Sydney, New South Wales 2006, Australia
| | - Robert J Vandenberg
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney , Sydney, New South Wales 2006, Australia
| | - Renae M Ryan
- Transporter Biology Group, Discipline of Pharmacology, Sydney Medical School, University of Sydney , Sydney, New South Wales 2006, Australia
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25
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Sharifian Gh M, Wilhelm MJ, Dai HL. Label-Free Optical Method for Quantifying Molecular Transport Across Cellular Membranes In Vitro. J Phys Chem Lett 2016; 7:3406-3411. [PMID: 27518496 DOI: 10.1021/acs.jpclett.6b01483] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate a nonlinear optical method for the label-free quantification of membrane transport rates of small/medium size molecules in living cells. Specifically, second-harmonic generation (SHG) laser scattering permits surface-specific characterization of transport across membranes. Unfortunately, most biologically relevant molecules are SHG-inactive. In the interest of extending this methodology for characterizing transport of any molecule, we monitor the SHG produced from an SHG-active reference molecule, in the presence of an SHG-inactive target molecule-of-interest as both molecules compete to cross a membrane. Of significance, the SHG-inactive target transport rate can be deduced as a perturbation in the measured transport rate of the reference. As proof-of-principle, we examine competitive transport of the strongly SHG-active cation, malachite green (MG), in the presence of a weakly SHG-active dication, propidium (Pro), across the outer-membrane protein channels in living bacteria. Comparison of the extracted and directly measured Pro transport rates validates the effectiveness of the method.
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Affiliation(s)
- Mohammad Sharifian Gh
- Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Michael J Wilhelm
- Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Hai-Lung Dai
- Department of Chemistry, Temple University , 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
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26
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LeVine MV, Cuendet MA, Khelashvili G, Weinstein H. Allosteric Mechanisms of Molecular Machines at the Membrane: Transport by Sodium-Coupled Symporters. Chem Rev 2016; 116:6552-87. [PMID: 26892914 DOI: 10.1021/acs.chemrev.5b00627] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Solute transport across cell membranes is ubiquitous in biology as an essential physiological process. Secondary active transporters couple the unfavorable process of solute transport against its concentration gradient to the energetically favorable transport of one or several ions. The study of such transporters over several decades indicates that their function involves complex allosteric mechanisms that are progressively being revealed in atomistic detail. We focus on two well-characterized sodium-coupled symporters: the bacterial amino acid transporter LeuT, which is the prototype for the "gated pore" mechanism in the mammalian synaptic monoamine transporters, and the archaeal GltPh, which is the prototype for the "elevator" mechanism in the mammalian excitatory amino acid transporters. We present the evidence for the role of allostery in the context of a quantitative formalism that can reconcile biochemical and biophysical data and thereby connects directly to recent insights into the molecular structure and dynamics of these proteins. We demonstrate that, while the structures and mechanisms of these transporters are very different, the available data suggest a common role of specific models of allostery in their functions. We argue that such allosteric mechanisms appear essential not only for sodium-coupled symport in general but also for the function of other types of molecular machines in the membrane.
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Affiliation(s)
- Michael V LeVine
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
| | - Michel A Cuendet
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
| | - George Khelashvili
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
| | - Harel Weinstein
- Department of Physiology and Biophysics, ‡HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University , New York, New York 10065, United States
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27
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Dynamic membrane protein topological switching upon changes in phospholipid environment. Proc Natl Acad Sci U S A 2015; 112:13874-9. [PMID: 26512118 DOI: 10.1073/pnas.1512994112] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A fundamental objective in membrane biology is to understand and predict how a protein sequence folds and orients in a lipid bilayer. Establishing the principles governing membrane protein folding is central to understanding the molecular basis for membrane proteins that display multiple topologies, the intrinsic dynamic organization of membrane proteins, and membrane protein conformational disorders resulting in disease. We previously established that lactose permease of Escherichia coli displays a mixture of topological conformations and undergoes postassembly bidirectional changes in orientation within the lipid bilayer triggered by a change in membrane phosphatidylethanolamine content, both in vivo and in vitro. However, the physiological implications and mechanism of dynamic structural reorganization of membrane proteins due to changes in lipid environment are limited by the lack of approaches addressing the kinetic parameters of transmembrane protein flipping. In this study, real-time fluorescence spectroscopy was used to determine the rates of protein flipping in the lipid bilayer in both directions and transbilayer flipping of lipids triggered by a change in proteoliposome lipid composition. Our results provide, for the first time to our knowledge, a dynamic picture of these events and demonstrate that membrane protein topological rearrangements in response to lipid modulations occur rapidly following a threshold change in proteoliposome lipid composition. Protein flipping was not accompanied by extensive lipid-dependent unfolding of transmembrane domains. Establishment of lipid bilayer asymmetry was not required but may accelerate the rate of protein flipping. Membrane protein flipping was found to accelerate the rate of transbilayer flipping of lipids.
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28
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He T, Gershenson A, Eyles SJ, Lee YJ, Liu WR, Wang J, Gao J, Roberts MF. Fluorinated Aromatic Amino Acids Distinguish Cation-π Interactions from Membrane Insertion. J Biol Chem 2015; 290:19334-42. [PMID: 26092728 DOI: 10.1074/jbc.m115.668343] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Indexed: 01/02/2023] Open
Abstract
Cation-π interactions, where protein aromatic residues supply π systems while a positive-charged portion of phospholipid head groups are the cations, have been suggested as important binding modes for peripheral membrane proteins. However, aromatic amino acids can also insert into membranes and hydrophobically interact with lipid tails. Heretofore there has been no facile way to differentiate these two types of interactions. We show that specific incorporation of fluorinated amino acids into proteins can experimentally distinguish cation-π interactions from membrane insertion of the aromatic side chains. Fluorinated aromatic amino acids destabilize the cation-π interactions by altering electrostatics of the aromatic ring, whereas their increased hydrophobicity enhances membrane insertion. Incorporation of pentafluorophenylalanine or difluorotyrosine into a Staphylococcus aureus phosphatidylinositol-specific phospholipase C variant engineered to contain a specific PC-binding site demonstrates the effectiveness of this methodology. Applying this methodology to the plethora of tyrosine residues in Bacillus thuringiensis phosphatidylinositol-specific phospholipase C definitively identifies those involved in cation-π interactions with phosphatidylcholine. This powerful method can easily be used to determine the roles of aromatic residues in other peripheral membrane proteins and in integral membrane proteins.
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Affiliation(s)
- Tao He
- From the Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003
| | - Stephen J Eyles
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003
| | - Yan-Jiun Lee
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, and
| | - Wenshe R Liu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, and
| | - Jiangyun Wang
- Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China
| | - Jianmin Gao
- From the Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467
| | - Mary F Roberts
- From the Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467,
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