1
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Sangeeta, Mishra SK, Bhattacherjee A. Role of Shape Deformation of DNA-Binding Sites in Regulating the Efficiency and Specificity in Their Recognition by DNA-Binding Proteins. JACS AU 2024; 4:2640-2655. [PMID: 39055163 PMCID: PMC11267559 DOI: 10.1021/jacsau.4c00393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 07/27/2024]
Abstract
Accurate transcription of genetic information is crucial, involving precise recognition of the binding motifs by DNA-binding proteins. While some proteins rely on short-range hydrophobic and hydrogen bonding interactions at binding sites, others employ a DNA shape readout mechanism for specific recognition. In this mechanism, variations in DNA shape at the binding motif resulted from either inherent flexibility or binding of proteins at adjacent sites are sensed and capitalized by the searching proteins to locate them specifically. Through extensive computer simulations, we investigate both scenarios to uncover the underlying mechanism and origin of specificity in the DNA shape readout mechanism. Our findings reveal that deformation in shape at the binding motif creates an entropy funnel, allowing information about altered shapes to manifest as fluctuations in minor groove widths. This signal enhances the efficiency of nonspecific search of nearby proteins by directing their movement toward the binding site, primarily driven by a gain in entropy. We propose this as a generic mechanism for DNA shape readout, where specificity arises from the alignment between the molecular frustration of the searching protein and the ruggedness of the entropic funnel governed by molecular features of the protein and arrangement of the DNA bases at the binding site, respectively.
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Affiliation(s)
- Sangeeta
- School of Computational & Integrative
Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sujeet Kumar Mishra
- School of Computational & Integrative
Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Arnab Bhattacherjee
- School of Computational & Integrative
Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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2
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Wang B, Tieleman DP. The structure, self-assembly and dynamics of lipid nanodiscs revealed by computational approaches. Biophys Chem 2024; 309:107231. [PMID: 38569455 DOI: 10.1016/j.bpc.2024.107231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 04/05/2024]
Abstract
Nanodisc technology is increasingly being used in structural, biochemical and biophysical studies of membrane proteins. The computational approaches have revealed many important features of nanodisc assembly, structures and dynamics. Therefore, we reviewed the application of computational approaches, especially molecular modeling and molecular dyncamics (MD) simulations, to characterize nanodiscs, including the structural models, assembly and disassembly, protocols for modeling, structural properties and dynamics, and protein-lipid interactions in nanodiscs. More amazing computational studies about nanodiscs are looked forward to in the future.
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Affiliation(s)
- Beibei Wang
- Centre for Advanced Materials Research, Beijing Normal University, Zhuhai 519087, China.
| | - D Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary T2N 1N4, Canada.
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3
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Gupta S, Soni J, Kumar A, Mandal T. Origin of the nonlinear structural and mechanical properties in oppositely curved lipid mixtures. J Chem Phys 2023; 159:165102. [PMID: 37873964 DOI: 10.1063/5.0167144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 10/04/2023] [Indexed: 10/25/2023] Open
Abstract
Structural and mechanical properties of membranes such as thickness, tail order, bending modulus and curvature energetics play crucial role in controlling various cellular functions that depend on the local lipid organization and membrane reshaping. While behavior of these biophysical properties are well understood in single component membranes, very little is known about how do they change in the mixed lipid membranes. Often various properties of the mixed lipid bilayers are assumed to change linearly with the mole fractions of the constituent lipids which, however, is true for "ideal" mixing only. In this study, using molecular dynamics simulations, we show that structural and mechanical properties of binary lipid mixture change nonlinearly with the lipid mole fractions, and the strength of the nonlinearity depends on two factors - spontaneous curvature difference and locally inhomogeneous interactions between the lipid components.
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Affiliation(s)
- Shivam Gupta
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Jatin Soni
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Awneesh Kumar
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Taraknath Mandal
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
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4
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Saini R, Debnath A. Thylakoid Composition Facilitates Chlorophyll a Dimerization through Stronger Interlipid Interactions. J Phys Chem B 2023; 127:9082-9094. [PMID: 37819861 DOI: 10.1021/acs.jpcb.3c04942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Plant thylakoid membrane serves as a crucial matrix for the aggregation of chlororophyll a (CLA) pigments, essential for light harvesting. To understand the role of lipid compositions in the stability of CLA aggregates, dimerization of chlorophyll a molecules (CLA) is studied in the presence of the thylakoid and the bilayers comprising either the least or the highest unsaturated lipids by using coarse-grained molecular dynamics simulations. The thylakoid membrane enhances the stability of the CLA dimer compared with other membranes due to very strong lipid-lipid interactions. The thylakoid exhibits a distinct distribution of lipids around the CLA dimer. Less unsaturated lipids reside in close proximity to the dimer, promoting increased order and efficient packing. Conversely, higher unsaturated lipids are depleted from the dimer, imparting flexibility to the membrane. The combination of tight packing near the dimer and membrane flexibility away from the dimer enhances the stability of the dimer in the thylakoid membrane. Our results suggest that lipid mixing, rather than lipid unsaturation, plays a critical role in facilitating CLA dimerization by modulating the membrane microenvironment through stronger lipid-lipid interactions. These insights will be useful in understanding how lipid compositions affect efficient light absorption and energy transfer during photosynthesis in the future.
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Affiliation(s)
- Renu Saini
- Department of Chemistry, Indian Institute of Technology, Jodhpur, Rajasthan 342030, India
| | - Ananya Debnath
- Department of Chemistry, Indian Institute of Technology, Jodhpur, Rajasthan 342030, India
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5
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Gómez-Fernández JC, Goñi FM. The Myth of The Annular Lipids. Biomedicines 2022; 10:2672. [PMID: 36359192 PMCID: PMC9687668 DOI: 10.3390/biomedicines10112672] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 10/20/2022] [Accepted: 10/21/2022] [Indexed: 12/08/2023] Open
Abstract
In the early 1970s, the existence of a "lipid annulus" stably surrounding the individual intrinsic protein molecules was proposed by several authors. They referred to a number of lipid molecules in slow exchange with the bulk lipid in the bilayer, i.e., more or less protein-bound, and more ordered than the bulk lipid. The annular lipids would control enzyme activity. This idea was uncritically accepted by most scientists working with intrinsic membrane proteins at the time, so that the idea operated like a myth in the field. However, in the following decade, hard spectroscopic and biochemical evidence showed that the proposed annular lipids were not immobilized for a sufficiently long time to influence enzyme or transporter activity, nor were they ordered by the protein. Surprisingly, forty years later, the myth survives, and the term 'annular lipid' is still in use, in a different, but even more illogical sense.
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Affiliation(s)
- Juan C. Gómez-Fernández
- Department of Biochemistry and Molecular Biology (A), Faculty of Veterinary Science, Universidad de Murcia, 30100 Murcia, Spain;
| | - Félix M. Goñi
- Instituto Biofisika (CSIC, UPV/EHU), Department of Biochemistry, University of the Basque Country, 48940 Leioa, Spain
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6
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You X, Thakur N, Ray AP, Eddy MT, Baiz CR. A comparative study of interfacial environments in lipid nanodiscs and vesicles. BIOPHYSICAL REPORTS 2022; 2. [PMID: 36176716 PMCID: PMC9518727 DOI: 10.1016/j.bpr.2022.100066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Membrane protein conformations and dynamics are driven by the protein-lipid interactions occurring within the local environment of the membrane. These environments remain challenging to accurately capture in structural and biophysical experiments using bilayers. Consequently, there is an increasing need for realistic cell-membrane mimetics for in vitro studies. Lipid nanodiscs provide certain advantages over vesicles for membrane protein studies. Nanodiscs are increasingly used for structural and spectroscopic characterization of membrane proteins. Despite the common use of nanodiscs, the interfacial environments of lipids confined to a ~10-nm diameter area have remained relatively underexplored. Here, we use ultrafast two-dimensional infrared spectroscopy and temperature-dependent infrared absorption measurements of the ester carbonyls to compare the interfacial hydrogen bond structure and dynamics in lipid nanodiscs of varying lipid compositions and sizes with ~100-nm vesicles. We examine the effects of lipid composition and nanodisc size. We found that nanodiscs and vesicles share largely similar lipid-water H-bond environments and interfacial dynamics. Differences in measured enthalpies of H-bonding suggest that H-bond dynamics in nanodiscs are modulated by the interaction between the annular lipids and the scaffold protein.
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7
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Gupta S, Mandal T. Simulation study of domain formation in a model bacterial membrane. Phys Chem Chem Phys 2022; 24:18133-18143. [PMID: 35856570 DOI: 10.1039/d2cp01873j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent experimental studies revealed that functional membrane microdomains (FMMs) are formed in prokaryotic cells which are structurally and functionally similar to the lipid rafts formed in eukaryotic cells. In this study, we employ coarse-grained molecular dynamics simulations to investigate the mechanism of domain formation and its physiochemical properties in a model methicillin-resistant staphylococcus aureus (MRSA) cell membrane. We find that domains are formed through lateral segregation of staphyloxanthin (STX), a carotenoid which shields the bacteria from the host's immune because of its antioxidant nature. Simulation results suggest that membrane integrity increases with the size of the domain, which is assessed by computing bond order parameter of the lipid tails, membrane expansion modulus and water permeability across the membrane. Various membrane domain proteins such as flotillin-like protein floA and penicillin binding protein (PBP2a) preferentially bind with the STX and accumulate in the membrane domain which is consistent with the recent experimental results.
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Affiliation(s)
- Shivam Gupta
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Taraknath Mandal
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016, India.
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8
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Photoprotective conformational dynamics of photosynthetic light-harvesting proteins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148543. [PMID: 35202576 DOI: 10.1016/j.bbabio.2022.148543] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/25/2022] [Accepted: 02/15/2022] [Indexed: 11/21/2022]
Abstract
Under high light conditions, excess energy can damage the machinery of oxygenic photosynthesis. Plants have evolved a series of photoprotective processes, including conformational changes of the light-harvesting complexes that activate dissipation of energy as heat. In this mini-review, we will summarize our recent work developing and applying single-molecule methods to investigate the conformational states of the light-harvesting complexes. Through these measurements, we identified dissipative conformations and how they depend on conditions that mimic high light. Our studies revealed an equilibrium between the light-harvesting and dissipative conformations, and that the nature of the equilibrium varies with cellular environment, between proteins, and between species. Finally, we conclude with an outlook on open questions and implications for photosynthetic yields.
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9
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Jeong C, Franklin R, Edler KJ, Vanommeslaeghe K, Krueger S, Curtis JE. Styrene-Maleic Acid Copolymer Nanodiscs to Determine the Shape of Membrane Proteins. J Phys Chem B 2022; 126:1034-1044. [PMID: 35089036 DOI: 10.1021/acs.jpcb.1c05050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lipid nanodiscs can be used to solubilize functional membrane proteins (MPs) in nativelike environments. Thus, they are promising reagents that have been proven useful to characterize MPs. Both protein and non-protein molecular belts have shown promise to maintain the structural integrity of MPs in lipid nanodiscs. Small-angle neutron scattering (SANS) can be used to determine low-resolution structures of proteins in solution, which can be enhanced through the use of contrast variation methods. We present theoretical contrast variation SANS results for protein and styrene-maleic acid copolymer (SMA) belt 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) nanodiscs with and without additional bound or transmembrane proteins. The predicted scattering properties are derived from atomistic molecular dynamics simulations to account for conformational fluctuations, and we determine deuterium-labeling conditions such that SANS intensity profiles only include contributions from the scattering of the MP of interest. We propose strategies to tune the neutron scattering length densities (SLDs) of the SMA and DMPC using selective deuterium labeling such that the SLD of the nanodisc becomes homogeneous and its scattering can essentially be eliminated in solvents containing an appropriate amount of D2O. These finely tuned labeled polymer-based nanodiscs are expected to be useful to extract the size and molecular shape information of MPs using SANS-based contrast variation experiments, and they can be used with MPs of any molecular weight.
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Affiliation(s)
- Cheol Jeong
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States.,Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996-1600, United States
| | - Ryan Franklin
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States
| | - Karen J Edler
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K
| | - Kenno Vanommeslaeghe
- Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling─FABI, Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium
| | - Susan Krueger
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States
| | - Joseph E Curtis
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, Maryland 20899, United States
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10
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MsbA: an ABC transporter paradigm. Biochem Soc Trans 2021; 49:2917-2927. [PMID: 34821931 DOI: 10.1042/bst20211030] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 10/27/2021] [Accepted: 11/03/2021] [Indexed: 12/27/2022]
Abstract
ATP-binding cassette (ABC) transporters play an important role in various cellular processes. They display a similar architecture and share a mechanism which couples ATP hydrolysis to substrate transport. However, in the light of current data and recent experimental progress, this protein superfamily appears as multifaceted as their broad substrate range. Among the prokaryotic ABC transporters, MsbA can serve as a paradigm for research in this field. It is located in the inner membrane of Gram-negative bacteria and functions as a floppase for the lipopolysaccharide (LPS) precursor core-LPS, which is involved in the biogenesis of the bacterial outer membrane. While MsbA shows high similarity to eukaryotic ABC transporters, its expression in Gram-negative bacteria makes it conveniently accessible for many experimental approaches from spectroscopy to 3D structure determination. As an essential protein for bacterial membrane integrity, MsbA has also become an attractive target for the development of novel antibiotics. Furthermore, it serves as a model for multidrug efflux pumps. Here we provide an overview of recent findings and their relevance to the field, highlight the potential of methods such as solid-state NMR and EPR spectroscopy and provide a perspective for future work.
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11
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Manna P, Davies T, Hoffmann M, Johnson MP, Schlau-Cohen GS. Membrane-dependent heterogeneity of LHCII characterized using single-molecule spectroscopy. Biophys J 2021; 120:3091-3102. [PMID: 34214527 DOI: 10.1016/j.bpj.2021.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/16/2021] [Accepted: 06/08/2021] [Indexed: 10/21/2022] Open
Abstract
In green plants, light harvesting complex of Photosystem II (LHCII) absorbs and transports excitation energy toward the photosynthetic reaction centers and serves as a site for energy-dependent nonphotochemical quenching (qE), the photoprotective dissipation of energy as heat. LHCII is thought to activate dissipation through conformational changes that change the photophysical behaviors. Understanding this balance requires a characterization of how the conformations of LHCII, and thus its photophysics, are influenced by individual factors within the membrane environment. Here, we used ensemble and single-molecule fluorescence to characterize the excited-state lifetimes and switching kinetics of LHCII embedded in nanodisc- and liposome-based model membranes of various sizes and lipid compositions. As the membrane area decreased, the quenched population and the rate of conformational dynamics both increased because of interactions with other proteins, the aqueous solution, and/or disordered lipids. Although the conformational states and dynamics were similar in both thylakoid and asolectin lipids, photodegradation increased with thylakoid lipids, likely because of their charge and pressure properties. Collectively, these findings demonstrate the ability of membrane environments to tune the conformations and photophysics of LHCII.
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Affiliation(s)
- Premashis Manna
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Thomas Davies
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
| | - Madeline Hoffmann
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Matthew P Johnson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
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12
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Kjølbye LR, De Maria L, Wassenaar TA, Abdizadeh H, Marrink SJ, Ferkinghoff-Borg J, Schiøtt B. General Protocol for Constructing Molecular Models of Nanodiscs. J Chem Inf Model 2021; 61:2869-2883. [PMID: 34048229 DOI: 10.1021/acs.jcim.1c00157] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nanodisc technology is increasingly being applied for structural and biophysical studies of membrane proteins. In this work, we present a general protocol for constructing molecular models of nanodiscs for molecular dynamics simulations. The protocol is written in python and based on geometric equations, making it fast and easy to modify, enabling automation and customization of nanodiscs in silico. The novelty being the ability to construct any membrane scaffold protein (MSP) variant fast and easy given only an input sequence. We validated and tested the protocol by simulating seven different nanodiscs of various sizes and with different membrane scaffold proteins, both circularized and noncircularized. The structural and biophysical properties were analyzed and shown to be in good agreement with previously reported experimental data and simulation studies.
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Affiliation(s)
- Lisbeth R Kjølbye
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark.,Novo Nordisk A/S, Novo Nordisk Park 1, 2760 Måløv, Denmark
| | | | - Tsjerk A Wassenaar
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Haleh Abdizadeh
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | | | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, Gustav Wieds vej 14, 8000 Aarhus C, Denmark
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13
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Abstract
The properties of natural lipid bilayers are vital to the regulation of many membrane proteins. Scaffolded nanodiscs provide an in vitro lipid bilayer platform to host membrane proteins in an environment that approximates native lipid bilayers. However, the properties of scaffold-enclosed bilayers may depart significantly from those of bulk cellular membranes. Therefore, to improve the usefulness of nanodiscs it is essential to understand the properties of lipids restricted by scaffolds. We used computational molecular dynamics and modeling approaches to understand the effects of nanodisc size, scaffold type (DNA or protein), and hydrophobic modification of DNA scaffolds on bilayer stability and degree to which the properties of enclosed bilayers approximate bulk bilayers. With respect to achieving bulk bilayer behavior, we found that charge neutralization of DNA scaffolds was more important than the total hydrophobic content of their modifications: bilayer properties were better for scaffolds having a large number of short alkyl chains than those having fewer long alkyl chains. Further, complete charge neutralization of DNA scaffolds enabled better lipid binding, and more stable bilayers, as shown by steered molecular dynamics simulations that measured the force required to dislodge scaffolds from lipid bilayer patches. Considered together, our simulations provide a guide to the design of DNA-scaffolded nanodiscs suitable for studying membrane proteins.
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Affiliation(s)
- Vishal Maingi
- Department of Bioengineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Paul W K Rothemund
- Departments of Bioengineering, Computing + Mathematical Sciences, and Computation & Neural Systems, California Institute of Technology, Pasadena, California 91125, United States
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14
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Iadanza MG, Schiffrin B, White P, Watson MA, Horne JE, Higgins AJ, Calabrese AN, Brockwell DJ, Tuma R, Kalli AC, Radford SE, Ranson NA. Distortion of the bilayer and dynamics of the BAM complex in lipid nanodiscs. Commun Biol 2020; 3:766. [PMID: 33318620 PMCID: PMC7736308 DOI: 10.1038/s42003-020-01419-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 10/12/2020] [Indexed: 11/28/2022] Open
Abstract
The β-barrel assembly machinery (BAM) catalyses the folding and insertion of β-barrel outer membrane proteins (OMPs) into the outer membranes of Gram-negative bacteria by mechanisms that remain unclear. Here, we present an ensemble of cryoEM structures of the E. coli BamABCDE (BAM) complex in lipid nanodiscs, determined using multi-body refinement techniques. These structures, supported by single-molecule FRET measurements, describe a range of motions in the BAM complex, mostly localised within the periplasmic region of the major subunit BamA. The β-barrel domain of BamA is in a 'lateral open' conformation in all of the determined structures, suggesting that this is the most energetically favourable species in this bilayer. Strikingly, the BAM-containing lipid nanodisc is deformed, especially around BAM's lateral gate. This distortion is also captured in molecular dynamics simulations, and provides direct structural evidence for the lipid 'disruptase' activity of BAM, suggested to be an important part of its functional mechanism.
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Affiliation(s)
- Matthew G Iadanza
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Bob Schiffrin
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Paul White
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Matthew A Watson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Anna J Higgins
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Roman Tuma
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - Antreas C Kalli
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
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15
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Bunker A, Róg T. Mechanistic Understanding From Molecular Dynamics Simulation in Pharmaceutical Research 1: Drug Delivery. Front Mol Biosci 2020; 7:604770. [PMID: 33330633 PMCID: PMC7732618 DOI: 10.3389/fmolb.2020.604770] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 11/02/2020] [Indexed: 12/12/2022] Open
Abstract
In this review, we outline the growing role that molecular dynamics simulation is able to play as a design tool in drug delivery. We cover both the pharmaceutical and computational backgrounds, in a pedagogical fashion, as this review is designed to be equally accessible to pharmaceutical researchers interested in what this new computational tool is capable of and experts in molecular modeling who wish to pursue pharmaceutical applications as a context for their research. The field has become too broad for us to concisely describe all work that has been carried out; many comprehensive reviews on subtopics of this area are cited. We discuss the insight molecular dynamics modeling has provided in dissolution and solubility, however, the majority of the discussion is focused on nanomedicine: the development of nanoscale drug delivery vehicles. Here we focus on three areas where molecular dynamics modeling has had a particularly strong impact: (1) behavior in the bloodstream and protective polymer corona, (2) Drug loading and controlled release, and (3) Nanoparticle interaction with both model and biological membranes. We conclude with some thoughts on the role that molecular dynamics simulation can grow to play in the development of new drug delivery systems.
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Affiliation(s)
- Alex Bunker
- Division of Pharmaceutical Biosciences, Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Tomasz Róg
- Department of Physics, University of Helsinki, Helsinki, Finland
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16
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Sligar SG, Denisov IG. Nanodiscs: A toolkit for membrane protein science. Protein Sci 2020; 30:297-315. [PMID: 33165998 DOI: 10.1002/pro.3994] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 10/30/2020] [Accepted: 10/30/2020] [Indexed: 12/25/2022]
Abstract
Membrane proteins are involved in numerous vital biological processes, including transport, signal transduction and the enzymes in a variety of metabolic pathways. Integral membrane proteins account for up to 30% of the human proteome and they make up more than half of all currently marketed therapeutic targets. Unfortunately, membrane proteins are inherently recalcitrant to study using the normal toolkit available to scientists, and one is most often left with the challenge of finding inhibitors, activators and specific antibodies using a denatured or detergent solubilized aggregate. The Nanodisc platform circumvents these challenges by providing a self-assembled system that renders typically insoluble, yet biologically and pharmacologically significant, targets such as receptors, transporters, enzymes, and viral antigens soluble in aqueous media in a native-like bilayer environment that maintain a target's functional activity. By providing a bilayer surface of defined composition and structure, Nanodiscs have found great utility in the study of cellular signaling complexes that assemble on a membrane surface. Nanodiscs provide a nanometer scale vehicle for the in vivo delivery of amphipathic drugs, therapeutic lipids, tethered nucleic acids, imaging agents and active protein complexes. This means for generating nanoscale lipid bilayers has spawned the successful use of numerous other polymer and peptide amphipathic systems. This review, in celebration of the Anfinsen Award, summarizes some recent results and provides an inroad into the current and historical literature.
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Affiliation(s)
- Stephen G Sligar
- Departments of Biochemistry Chemistry, University of Illinois, Urbana-Champaign, Urbana, Illinois, USA
| | - Ilia G Denisov
- Departments of Biochemistry Chemistry, University of Illinois, Urbana-Champaign, Urbana, Illinois, USA
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17
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Complexity of seemingly simple lipid nanodiscs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183420. [DOI: 10.1016/j.bbamem.2020.183420] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 06/26/2020] [Accepted: 07/07/2020] [Indexed: 12/15/2022]
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18
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Schachter I, Allolio C, Khelashvili G, Harries D. Confinement in Nanodiscs Anisotropically Modifies Lipid Bilayer Elastic Properties. J Phys Chem B 2020; 124:7166-7175. [PMID: 32697588 PMCID: PMC7526989 DOI: 10.1021/acs.jpcb.0c03374] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
![]()
Lipid
nanodiscs are small synthetic lipid bilayer structures that
are stabilized in solution by special circumscribing (or scaffolding)
proteins or polymers. Because they create native-like environments
for transmembrane proteins, lipid nanodiscs have become a powerful
tool for structural determination of this class of systems when combined
with cryo-electron microscopy or nuclear magnetic resonance. The elastic
properties of lipid bilayers determine how the lipid environment responds
to membrane protein perturbations, and how the lipid in turn modifies
the conformational state of the embedded protein. However, despite
the abundant use of nanodiscs in determining membrane protein structure,
the elastic material properties of even pure lipid nanodiscs (i.e.,
without embedded proteins) have not yet been quantitatively investigated.
A major hurdle is due to the inherently nonlocal treatment of the
elastic properties of lipid systems implemented by most existing methods,
both experimental and computational. In addition, these methods are
best suited for very large “infinite” size lipidic assemblies,
or ones that contain periodicity, in the case of simulations. We have
previously described a computational analysis of molecular dynamics
simulations designed to overcome these limitations, so it allows quantification
of the bending rigidity (KC) and tilt
modulus (κt) on a local scale even for finite, nonperiodic
systems, such as lipid nanodiscs. Here we use this computational approach
to extract values of KC and κt for a set of lipid nanodisc systems that vary in size and
lipid composition. We find that the material properties of lipid nanodiscs
are different from those of infinite bilayers of corresponding lipid
composition, highlighting the effect of nanodisc confinement. Nanodiscs
tend to show higher stiffness than their corresponding macroscopic
bilayers, and moreover, their material properties vary spatially within
them. For small-size MSP1 nanodiscs, the stiffness decreases radially,
from a value that is larger in their center than the moduli of the
corresponding bilayers by a factor of ∼2–3. The larger
nanodiscs (MSP1E3D1 and MSP2N2) show milder spatial changes of moduli
that are composition dependent and can be maximal in the center or
at some distance from it. These trends in moduli correlate with spatially
varying structural properties, including the area per lipid and the
nanodisc thickness. Finally, as has previously been reported, nanodiscs
tend to show deformations from perfectly flat circular geometries
to varying degrees, depending on size and lipid composition. The modulations
of lipid elastic properties that we find should be carefully considered
when making structural and functional inferences concerning embedded
proteins.
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Affiliation(s)
- Itay Schachter
- Institute of Chemistry, the Fritz Haber Research Center, and the Harvey M. Kruger center for Nanoscience & Nanotechnology, The Hebrew University, Jerusalem 9190401, Israel
| | - Christoph Allolio
- Institute of Mathematics, Faculty of Mathematics and Physics, Charles University, Prague 18674, Czech Republic
| | - George Khelashvili
- Department of Physiology and Biophysics, Weill Cornell Medical College of Cornell University, New York, New York 10065, United States.,Institute for Computational Biomedicine, Weill Cornell Medical College of Cornell University, New York, New York 10065, United States
| | - Daniel Harries
- Institute of Chemistry, the Fritz Haber Research Center, and the Harvey M. Kruger center for Nanoscience & Nanotechnology, The Hebrew University, Jerusalem 9190401, Israel
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19
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McLean MA, Denisov IG, Grinkova YV, Sligar SG. Dark, Ultra-Dark and Ultra-Bright Nanodiscs for membrane protein investigations. Anal Biochem 2020; 607:113860. [PMID: 32750355 DOI: 10.1016/j.ab.2020.113860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/02/2020] [Accepted: 07/03/2020] [Indexed: 11/16/2022]
Abstract
We describe the construction, expression and purification of three new membrane scaffold proteins (MSP) for use in assembling Nanodiscs. These new MSPs have a variety of luminescent properties for use in combination with several analytical methods. "Dark" MSP has no tryptophan residues, "Ultra-Dark" replaces both tryptophan and tyrosine with non-fluorescent side chains, and "Ultra-Bright" adds additional tryptophans to the parent membrane scaffold protein to provide a dramatic increase in native tryptophan fluorescence. All MSPs were used to successfully assemble Nanodiscs nominally 10 nm in diameter, and the resultant bilayer structure was characterized. An example of the usefulness of these new scaffold proteins is provided.
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Affiliation(s)
- Mark A McLean
- Department of Biochemistry, University of Illinois, Urbana, IL, 16801, USA
| | - Ilia G Denisov
- Department of Biochemistry, University of Illinois, Urbana, IL, 16801, USA
| | - Yelena V Grinkova
- Department of Biochemistry, University of Illinois, Urbana, IL, 16801, USA
| | - Stephen G Sligar
- Department of Biochemistry, University of Illinois, Urbana, IL, 16801, USA; Department of Chemistry, University of Illinois, Urbana, IL, 16801, USA.
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20
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Bengtsen T, Holm VL, Kjølbye LR, Midtgaard SR, Johansen NT, Tesei G, Bottaro S, Schiøtt B, Arleth L, Lindorff-Larsen K. Structure and dynamics of a nanodisc by integrating NMR, SAXS and SANS experiments with molecular dynamics simulations. eLife 2020; 9:e56518. [PMID: 32729831 PMCID: PMC7426092 DOI: 10.7554/elife.56518] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 07/28/2020] [Indexed: 12/16/2022] Open
Abstract
Nanodiscs are membrane mimetics that consist of a protein belt surrounding a lipid bilayer, and are broadly used for characterization of membrane proteins. Here, we investigate the structure, dynamics and biophysical properties of two small nanodiscs, MSP1D1ΔH5 and ΔH4H5. We combine our SAXS and SANS experiments with molecular dynamics simulations and previously obtained NMR and EPR data to derive and validate a conformational ensemble that represents the structure and dynamics of the nanodisc. We find that it displays conformational heterogeneity with various elliptical shapes, and with substantial differences in lipid ordering in the centre and rim of the discs. Together, our results reconcile previous apparently conflicting observations about the shape of nanodiscs, and pave the way for future integrative studies of larger complex systems such as membrane proteins embedded in nanodiscs.
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Affiliation(s)
- Tone Bengtsen
- Structural Biology and NMR Laboratory and Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of CopenhagenCopenhagenDenmark
| | - Viktor L Holm
- Structural Biophysics, X-ray and Neutron Science, Niels Bohr Institute, University of CopenhagenCopenhagenDenmark
| | | | - Søren R Midtgaard
- Structural Biophysics, X-ray and Neutron Science, Niels Bohr Institute, University of CopenhagenCopenhagenDenmark
| | - Nicolai Tidemand Johansen
- Structural Biophysics, X-ray and Neutron Science, Niels Bohr Institute, University of CopenhagenCopenhagenDenmark
| | - Giulio Tesei
- Structural Biology and NMR Laboratory and Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of CopenhagenCopenhagenDenmark
| | - Sandro Bottaro
- Structural Biology and NMR Laboratory and Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of CopenhagenCopenhagenDenmark
| | | | - Lise Arleth
- Structural Biophysics, X-ray and Neutron Science, Niels Bohr Institute, University of CopenhagenCopenhagenDenmark
| | - Kresten Lindorff-Larsen
- Structural Biology and NMR Laboratory and Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of CopenhagenCopenhagenDenmark
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21
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Camp T, Sligar SG. Nanodisc self-assembly is thermodynamically reversible and controllable. SOFT MATTER 2020; 16:5615-5623. [PMID: 32524103 PMCID: PMC7338007 DOI: 10.1039/d0sm00336k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Many highly ordered complex systems form by the spontaneous self-assembly of simpler subunits. An important biophysical tool that relies on self-assembly is the Nanodisc system, which finds extensive use as native-like environments for studying membrane proteins. Nanodiscs are self-assembled from detergent-solubilized mixtures of phospholipids and engineered helical proteins called membrane scaffold proteins (MSPs). Detergent removal results in the formation of nanoscale bilayers stabilized by two MSP "belts." Despite their numerous applications in biology, and contributions from many laboratories world-wide, little is known about the self-assembly process such as when the bilayer forms or when the MSP associates with lipids. We use fluorescence and optical spectroscopy to probe self-assembly at various equilibria defined by the detergent concentration. We show that the bilayer begins forming below the critical micellar concentration of the detergent (10 mM), and the association of MSP and lipids begins at lower detergent levels, showing a dependence on the concentrations of MSP and lipids. Following the dissolution process by adding detergent to purified Nanodiscs demonstrates that the self-assembly is reversible. Our data demonstrate that Nanodisc self-assembly is experimentally accessible, and that controlling the detergent concentration allows exquisite control over the self-assembly reaction. This improved understanding of self-assembly could lead to better functional incorporation of hitherto intractable membrane target proteins.
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Affiliation(s)
- Tyler Camp
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Stephen G Sligar
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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22
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Licari G, Strakova K, Matile S, Tajkhorshid E. Twisting and tilting of a mechanosensitive molecular probe detects order in membranes. Chem Sci 2020; 11:5637-5649. [PMID: 32864081 PMCID: PMC7433777 DOI: 10.1039/d0sc02175j] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 04/29/2020] [Indexed: 12/29/2022] Open
Abstract
Lateral forces in biological membranes affect a variety of dynamic cellular processes. Recent synthetic efforts have introduced fluorescent "flippers" as environment-sensitive planarizable push-pull probes that can detect lipid packing and membrane tension, and respond to lipid-induced mechanical forces by a shift in their spectroscopic properties. Herein, we investigate the molecular origin of the mechanosensitivity of the best known flipper, Flipper-TR, by an extended set of molecular dynamics (MD) simulations in membranes of increasing complexity and under different physicochemical conditions, revealing unprecedented details of the sensing process. Simulations enabled by accurate refinement of Flipper-TR force field using quantum mechanical calculations allowed us to unambiguously correlate the planarization of the two fluorescent flippers to spectroscopic response. In particular, Flipper-TR conformation exhibits bimodal distribution in disordered membranes and a unimodal distribution in highly ordered membranes. Such dramatic change was associated with a shift in Flipper-TR excitation spectra, as supported both by our simulated and experimentally-measured spectra. Flipper-TR sensitivity to phase-transition is confirmed by a temperature-jump protocol that alters the lipid phase of an ordered membrane, triggering an instantaneous mechanical twisting of the probe. Simulations show that the probe is also sensitive to surface tension, since even in a naturally disordered membrane, the unimodal distribution of coplanar flippers can be achieved if a sufficiently negative surface tension is applied to the membrane. MD simulations in ternary mixtures containing raft-like nanodomains show that the probe can discriminate lipid domains in phase-separated complex bilayers. A histogram-based approach, called DOB-phase classification, is introduced that can differentiate regions of disordered and ordered lipid phases by comparing dihedral distributions of Flipper-TR. Moreover, a new sensing mechanism involving the orientation of Flipper-TR is elucidated, corroborating experimental evidence that the probe tilt angle is strongly dependent on lipid ordering. The obtained atomic-resolution description of Flipper-TR mechanosensitivity is key to the interpretation of experimental data and to the design of novel mechanosensors with improved spectroscopic properties.
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Affiliation(s)
- Giuseppe Licari
- NIH Center for Macromolecular Modeling and Bioinformatics , Beckman Institute for Advanced Science and Technology , Department of Biochemistry , Center for Biophysics and Quantitative Biology , University of Illinois at Urbana-Champaign , Urbana , Illinois , USA . ; Tel: +1-217-244-6914
| | - Karolina Strakova
- School of Chemistry and Biochemistry , National Centre of Competence in Research (NCCR) Chemical Biology , University of Geneva , Geneva , Switzerland
| | - Stefan Matile
- School of Chemistry and Biochemistry , National Centre of Competence in Research (NCCR) Chemical Biology , University of Geneva , Geneva , Switzerland
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics , Beckman Institute for Advanced Science and Technology , Department of Biochemistry , Center for Biophysics and Quantitative Biology , University of Illinois at Urbana-Champaign , Urbana , Illinois , USA . ; Tel: +1-217-244-6914
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23
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Abstract
The interactions between lipids and proteins are one of the most fundamental processes in living organisms, responsible for critical cellular events ranging from replication, cell division, signaling, and movement. Enabling the central coupling responsible for maintaining the functionality of the breadth of proteins, receptors, and enzymes that find their natural home in biological membranes, the fundamental mechanisms of recognition of protein for lipid, and vice versa, have been a focal point of biochemical and biophysical investigations for many decades. Complexes of lipids and proteins, such as the various lipoprotein factions, play central roles in the trafficking of important proteins, small molecules and metabolites and are often implicated in disease states. Recently an engineered lipoprotein particle, termed the nanodisc, a modified form of the human high density lipoprotein fraction, has served as a membrane mimetic for the investigation of membrane proteins and studies of lipid-protein interactions. In this review, we summarize the current knowledge regarding this self-assembling lipid-protein complex and provide examples for its utility in the investigation of a large number of biological systems.
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24
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Heterogeneity in structure and dynamics of water near bilayers using TIP3P and TIP4P/2005 water models. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.110396] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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25
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López CA, Swift MF, Xu XP, Hanein D, Volkmann N, Gnanakaran S. Biophysical Characterization of a Nanodisc with and without BAX: An Integrative Study Using Molecular Dynamics Simulations and Cryo-EM. Structure 2019; 27:988-999.e4. [DOI: 10.1016/j.str.2019.03.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 12/21/2018] [Accepted: 03/15/2019] [Indexed: 10/27/2022]
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26
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Sahoo BR, Genjo T, Moharana KC, Ramamoorthy A. Self-Assembly of Polymer-Encased Lipid Nanodiscs and Membrane Protein Reconstitution. J Phys Chem B 2019; 123:4562-4570. [DOI: 10.1021/acs.jpcb.9b03681] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - Kanhu C. Moharana
- Department of Bioinformatics, Orissa University of Agriculture and Technology, Bhubaneswar, Odisha 751003, India
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27
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Xue M, Cheng L, Faustino I, Guo W, Marrink SJ. Molecular Mechanism of Lipid Nanodisk Formation by Styrene-Maleic Acid Copolymers. Biophys J 2018; 115:494-502. [PMID: 29980293 PMCID: PMC6084417 DOI: 10.1016/j.bpj.2018.06.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/02/2018] [Accepted: 06/11/2018] [Indexed: 01/06/2023] Open
Abstract
Experimental characterization of membrane proteins often requires solubilization. A recent approach is to use styrene-maleic acid (SMA) copolymers to isolate membrane proteins in nanometer-sized membrane disks, or so-called SMA lipid particles (SMALPs). The approach has the advantage of allowing direct extraction of proteins, keeping their native lipid environment. Despite the growing popularity of using SMALPs, the molecular mechanism behind the process remains poorly understood. Here, we unravel the molecular details of the nanodisk formation by using coarse-grained molecular dynamics simulations. We show how SMA copolymers bind to the lipid bilayer interface, driven by the hydrophobic effect. Due to the concerted action of multiple adsorbed copolymers, large membrane defects appear, including small, water-filled pores. The copolymers can stabilize the rim of these pores, leading to pore growth and membrane disruption. Although complete solubilization is not seen on the timescale of our simulations, self-assembly experiments show that small nanodisks are the thermodynamically preferred end state. Our findings shed light on the mechanism of SMALP formation and on their molecular structure. This can be an important step toward the design of optimized extraction tools for membrane protein research.
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Affiliation(s)
- Minmin Xue
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education, Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China; Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Lisheng Cheng
- College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing, People's Republic of China
| | - Ignacio Faustino
- Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Wanlin Guo
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education, Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing, People's Republic of China
| | - Siewert J Marrink
- Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, the Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
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28
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Molecular dynamics simulations of lipid nanodiscs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2094-2107. [PMID: 29729280 DOI: 10.1016/j.bbamem.2018.04.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 04/27/2018] [Accepted: 04/28/2018] [Indexed: 01/02/2023]
Abstract
A lipid nanodisc is a discoidal lipid bilayer stabilized by proteins, peptides, or polymers on its edge. Nanodiscs have two important connections to structural biology. The first is associated with high-density lipoprotein (HDL), a particle with a variety of functionalities including lipid transport. Nascent HDL (nHDL) is a nanodisc stabilized by Apolipoprotein A-I (APOA1). Determining the structure of APOA1 and its mimetic peptides in nanodiscs is crucial to understanding pathologies related to HDL maturation and designing effective therapies. Secondly, nanodiscs offer non-detergent membrane-mimicking environments and greatly facilitate structural studies of membrane proteins. Although seemingly similar, natural and synthetic nanodiscs are different in that nHDL is heterogeneous in size, due to APOA1 elasticity, and gradually matures to become spherical. Synthetic nanodiscs, in contrast, should be homogenous, stable, and size-tunable. This report reviews previous molecular dynamics (MD) simulation studies of nanodiscs and illustrates convergence and accuracy issues using results from new multi-microsecond atomistic MD simulations. These new simulations reveal that APOA1 helices take 10-20 μs to rearrange on the nanodisc, while peptides take 2 μs to migrate from the disc surfaces to the edge. These systems can also become kinetically trapped depending on the initial conditions. For example, APOA1 was trapped in a biologically irrelevant conformation for the duration of a 10 μs trajectory; the peptides were similarly trapped for 5 μs. It therefore remains essential to validate MD simulations of these systems with experiments due to convergence and accuracy issues. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
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29
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Ermakova E, Zuev Y. Effect of ergosterol on the fungal membrane properties. All-atom and coarse-grained molecular dynamics study. Chem Phys Lipids 2017; 209:45-53. [PMID: 29122611 DOI: 10.1016/j.chemphyslip.2017.11.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 10/27/2017] [Accepted: 11/04/2017] [Indexed: 01/04/2023]
Abstract
Cell membranes are complex multicomponent systems consisting of thousands of different lipids with numerous embedded membrane proteins and many types of sterols. We used all-atom and coarse-grained molecular dynamics simulations to study the structural and dynamical properties of phospholipid bilayers containing four types of phospholipids and different amount of ergosterol, main sterol component in the fungal membranes. To characterize the influence of ergosterol on the membrane properties we analyzed the surface area per lipid, bilayer thickness, area compressibility modulus, mass density profiles, deuterium order parameters, and lateral diffusion coefficients. The presence of ergosterol induces the ordering of lipids leading to their denser packing, to reducing the lateral diffusion of lipids and lipid surface area, to increasing the thickness of bilayer and compressibility modulus. In addition, we evaluated each calculated property between the two simulation methods.
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Affiliation(s)
- Elena Ermakova
- Kazan Institute of Biochemistry and Biophysics RAS, Kazan, 420111, Russian Federation.
| | - Yuriy Zuev
- Kazan Institute of Biochemistry and Biophysics RAS, Kazan, 420111, Russian Federation; Kazan State Power Engineering University, Kazan, 420066, Russian Federation
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30
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Abstract
Membrane proteins play a most important part in metabolism, signaling, cell motility, transport, development, and many other biochemical and biophysical processes which constitute fundamentals of life on the molecular level. Detailed understanding of these processes is necessary for the progress of life sciences and biomedical applications. Nanodiscs provide a new and powerful tool for a broad spectrum of biochemical and biophysical studies of membrane proteins and are commonly acknowledged as an optimal membrane mimetic system that provides control over size, composition, and specific functional modifications on the nanometer scale. In this review we attempted to combine a comprehensive list of various applications of nanodisc technology with systematic analysis of the most attractive features of this system and advantages provided by nanodiscs for structural and mechanistic studies of membrane proteins.
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Affiliation(s)
- Ilia G Denisov
- Department of Biochemistry and Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States
| | - Stephen G Sligar
- Department of Biochemistry and Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States
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31
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Simonsen JB. Evaluation of reconstituted high-density lipoprotein (rHDL) as a drug delivery platform – a detailed survey of rHDL particles ranging from biophysical properties to clinical implications. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2016; 12:2161-2179. [DOI: 10.1016/j.nano.2016.05.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 05/02/2016] [Accepted: 05/05/2016] [Indexed: 12/15/2022]
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32
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Lu Y, Zhang H, Niedzwiedzki DM, Jiang J, Blankenship RE, Gross ML. Fast Photochemical Oxidation of Proteins Maps the Topology of Intrinsic Membrane Proteins: Light-Harvesting Complex 2 in a Nanodisc. Anal Chem 2016; 88:8827-34. [PMID: 27500903 PMCID: PMC5201186 DOI: 10.1021/acs.analchem.6b01945] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Although membrane proteins are crucial participants in photosynthesis and other biological processes, many lack high-resolution structures. Prior to achieving a high-resolution structure, we are investigating whether MS-based footprinting can provide coarse-grained protein structure by following structural changes that occur upon ligand binding, pH change, and membrane binding. Our platform probes topology and conformation of membrane proteins by combining MS-based footprinting, specifically fast photochemical oxidation of proteins (FPOP), and lipid Nanodiscs, which are more similar to the native membrane environment than are the widely used detergent micelles. We describe here results that show a protein's outer membrane regions are more heavily footprinted by OH radicals whereas the regions spanning the lipid bilayer remain inert to the labeling. Nanodiscs generally exhibit more protection of membrane proteins compared to detergent micelles and less shielding to those protein residues that exist outside the membrane. The combination of immobilizing the protein in Nanodiscs and footprinting with FPOP is a feasible approach to map extra-membrane protein surfaces, even at the amino-acid level, and to illuminate intrinsic membrane protein topology.
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Affiliation(s)
- Yue Lu
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Hao Zhang
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Dariusz M. Niedzwiedzki
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Jing Jiang
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Robert E. Blankenship
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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33
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Prieß M, Schäfer LV. Release of Entropic Spring Reveals Conformational Coupling Mechanism in the ABC Transporter BtuCD-F. Biophys J 2016; 110:2407-2418. [PMID: 27276259 PMCID: PMC4906252 DOI: 10.1016/j.bpj.2016.04.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 03/30/2016] [Accepted: 04/20/2016] [Indexed: 01/14/2023] Open
Abstract
Substrate translocation by ATP-binding cassette (ABC) transporters involves coupling of ATP binding and hydrolysis in the nucleotide-binding domains (NBDs) to conformational changes in the transmembrane domains. We used molecular dynamics simulations to investigate the atomic-level mechanism of conformational coupling in the ABC transporter BtuCD-F, which imports vitamin B12 across the inner membrane of Escherichia coli. Our simulations show how an engineered disulfide bond across the NBD dimer interface reduces conformational fluctuations and hence configurational entropy. As a result, the disulfide bond is under substantial mechanical stress. Releasing this entropic spring, as is the case in the wild-type transporter, combined with analyzing the pairwise forces between individual residues, unravels the coupling mechanism. The identified pathways along which force is propagated from the NBDs via the coupling helix to the transmembrane domains are composed of highly conserved residues, underlining their functional relevance. This study not only reveals the details of conformational coupling in BtuCD-F, it also provides a promising approach to other long-range conformational couplings, e.g., in ABC exporters or other ATP-driven molecular machines.
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Affiliation(s)
- Marten Prieß
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University, Bochum, Germany
| | - Lars V Schäfer
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University, Bochum, Germany.
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34
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Lee SC, Khalid S, Pollock NL, Knowles TJ, Edler K, Rothnie AJ, R T Thomas O, Dafforn TR. Encapsulated membrane proteins: A simplified system for molecular simulation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2549-2557. [PMID: 26946242 DOI: 10.1016/j.bbamem.2016.02.039] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 02/23/2016] [Accepted: 02/25/2016] [Indexed: 12/19/2022]
Abstract
Over the past 50years there has been considerable progress in our understanding of biomolecular interactions at an atomic level. This in turn has allowed molecular simulation methods employing full atomistic modelling at ever larger scales to develop. However, some challenging areas still remain where there is either a lack of atomic resolution structures or where the simulation system is inherently complex. An area where both challenges are present is that of membranes containing membrane proteins. In this review we analyse a new practical approach to membrane protein study that offers a potential new route to high resolution structures and the possibility to simplify simulations. These new approaches collectively recognise that preservation of the interaction between the membrane protein and the lipid bilayer is often essential to maintain structure and function. The new methods preserve these interactions by producing nano-scale disc shaped particles that include bilayer and the chosen protein. Currently two approaches lead in this area: the MSP system that relies on peptides to stabilise the discs, and SMALPs where an amphipathic styrene maleic acid copolymer is used. Both methods greatly enable protein production and hence have the potential to accelerate atomic resolution structure determination as well as providing a simplified format for simulations of membrane protein dynamics. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Sarah C Lee
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Syma Khalid
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - Naomi L Pollock
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Tim J Knowles
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Karen Edler
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Alice J Rothnie
- School of Life & Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Owen R T Thomas
- School of Chemical Engineering, College of Engineering and Physical Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Timothy R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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35
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Vestergaard M, Kraft JF, Vosegaard T, Thøgersen L, Schiøtt B. Bicelles and Other Membrane Mimics: Comparison of Structure, Properties, and Dynamics from MD Simulations. J Phys Chem B 2015; 119:15831-43. [PMID: 26610232 DOI: 10.1021/acs.jpcb.5b08463] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The increased interest in studying membrane proteins has led to the development of new membrane mimics such as bicelles and nanodiscs. However, only limited knowledge is available of how these membrane mimics are affected by embedded proteins and how well they mimic a lipid bilayer. Herein, we present molecular dynamics simulations to elucidate structural and dynamic properties of small bicelles and compare them to a large alignable bicelle, a small nanodisc, and a lipid bilayer. Properties such as lipid packing and properties related to embedding both an α-helical peptide and a transmembrane protein are investigated. The small bicelles are found to be very dynamic and mainly assume a prolate shape substantiating that small bicelles cannot be regarded as well-defined disclike structures. However, addition of a peptide results in an increased tendency to form disc-shaped bicelles. The small bicelles and the nanodiscs show increased peptide solvation and difference in peptide orientation compared to embedding in a bilayer. The large bicelle imitated a bilayer well with respect to both curvature and peptide solvation, although peripheral binding of short tailed lipids to the embedded proteins is observed, which could hinder ligand binding or multimer formation.
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Affiliation(s)
- Mikkel Vestergaard
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), and Department of Chemistry, Aarhus University , Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Johan F Kraft
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), and Department of Chemistry, Aarhus University , Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Thomas Vosegaard
- Danish Center for Ultrahigh-Field NMR Spectroscopy and Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
| | - Lea Thøgersen
- Center for Membrane Pumps in Cells and Disease (PUMPKIN), Bioinformatics Research Centre, Aarhus University , C.F. Møllers Alle 8, DK-8000 Aarhus C, Denmark
| | - Birgit Schiøtt
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), and Department of Chemistry, Aarhus University , Langelandsgade 140, DK-8000 Aarhus C, Denmark
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