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Dutagaci B, Sayadi M, Feig M. Heterogeneous dielectric generalized Born model with a van der Waals term provides improved association energetics of membrane-embedded transmembrane helices. J Comput Chem 2017; 38:1308-1320. [PMID: 28160300 DOI: 10.1002/jcc.24691] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 10/18/2016] [Accepted: 11/17/2016] [Indexed: 11/07/2022]
Abstract
The heterogeneous dielectric generalized Born (HDGB) implicit membrane formalism is extended by the addition of a van der Waals dispersion term to better describe the nonpolar components of the free energy of solvation. The new model, termed HDGBvdW, improves the energy estimates in the hydrophobic interior of the membrane, where polar and charged species are rarely found and nonpolar interactions become significant. The implicit van der Waals term for the membrane environment extends the model from Gallicchio et al. (J. Comput. Chem. 2004, 25, 479) by combining separate contributions from each of the membrane components. The HDGBvdW model is validated with a series of test cases ranging from membrane insertion and pair association profiles of amino acid side chain analogs and transmembrane helices. Overall, the HDGBvdW model leads to increased agreement with explicit membrane simulation results and experimental data. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Bercem Dutagaci
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, 48824
| | - Maryam Sayadi
- Department of Chemistry, Michigan State University, East Lansing, Michigan, 48824
| | - Michael Feig
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, 48824
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2
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Abstract
Transmembrane (TM) helices of integral membrane proteins can facilitate strong and specific noncovalent protein-protein interactions. Mutagenesis and structural analyses have revealed numerous examples in which the interaction between TM helices of single-pass membrane proteins is dependent on a GxxxG or (small)xxx(small) motif. It is therefore tempting to use the presence of these simple motifs as an indicator of TM helix interactions. In this Current Topic review, we point out that these motifs are quite common, with more than 50% of single-pass TM domains containing a (small)xxx(small) motif. However, the actual interaction strength of motif-containing helices depends strongly on sequence context and membrane properties. In addition, recent studies have revealed several GxxxG-containing TM domains that interact via alternative interfaces involving hydrophobic, polar, aromatic, or even ionizable residues that do not form recognizable motifs. In multipass membrane proteins, GxxxG motifs can be important for protein folding, and not just oligomerization. Our current knowledge thus suggests that the presence of a GxxxG motif alone is a weak predictor of protein dimerization in the membrane.
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Affiliation(s)
- Mark G Teese
- Lehrstuhl für Chemie der Biopolymere, Technische Universität München , 85354 Freising, Germany.,Center for Integrated Protein Science Munich (CIPSM) , 81377 Munich, Germany
| | - Dieter Langosch
- Lehrstuhl für Chemie der Biopolymere, Technische Universität München , 85354 Freising, Germany.,Center for Integrated Protein Science Munich (CIPSM) , 81377 Munich, Germany
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3
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Chavent M, Chetwynd AP, Stansfeld PJ, Sansom MSP. Dimerization of the EphA1 receptor tyrosine kinase transmembrane domain: Insights into the mechanism of receptor activation. Biochemistry 2014; 53:6641-52. [PMID: 25286141 PMCID: PMC4298228 DOI: 10.1021/bi500800x] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
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EphA1
is a receptor tyrosine kinase (RTK) that plays a key role
in developmental processes, including guidance of the migration of
axons and cells in the nervous system. EphA1, in common with other
RTKs, contains an N-terminal extracellular domain, a single transmembrane
(TM) α-helix, and a C-terminal intracellular kinase domain.
The TM helix forms a dimer, as seen in recent NMR studies. We have
modeled the EphA1 TM dimer using a multiscale approach combining coarse-grain
(CG) and atomistic molecular dynamics (MD) simulations. The one-dimensional
potential of mean force (PMF) for this system, based on interhelix
separation, has been calculated using CG MD simulations. This provides
a view of the free energy landscape for helix–helix interactions
of the TM dimer in a lipid bilayer. The resulting PMF profiles suggest
two states, consistent with a rotation-coupled activation mechanism.
The more stable state corresponds to a right-handed helix dimer interacting
via an N-terminal glycine zipper motif, consistent with a recent NMR
structure (2K1K). A second metastable state corresponds to a structure in which
the glycine zipper motif is not involved. Analysis of unrestrained
CG MD simulations based on representative models from the PMF calculations
or on the NMR structure reveals possible pathways of interconversion
between these two states, involving helix rotations about their long
axes. This suggests that the interaction of TM helices in EphA1 dimers
may be intrinsically dynamic. This provides a potential mechanism
for signaling whereby extracellular events drive a shift in the repopulation
of the underlying TM helix dimer energy landscape.
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Affiliation(s)
- Matthieu Chavent
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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4
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Sharonov GV, Bocharov EV, Kolosov PM, Astapova MV, Arseniev AS, Feofanov AV. Point mutations in dimerization motifs of the transmembrane domain stabilize active or inactive state of the EphA2 receptor tyrosine kinase. J Biol Chem 2014; 289:14955-64. [PMID: 24733396 DOI: 10.1074/jbc.m114.558783] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The EphA2 receptor tyrosine kinase plays a central role in the regulation of cell adhesion and guidance in many human tissues. The activation of EphA2 occurs after proper dimerization/oligomerization in the plasma membrane, which occurs with the participation of extracellular and cytoplasmic domains. Our study revealed that the isolated transmembrane domain (TMD) of EphA2 embedded into the lipid bicelle dimerized via the heptad repeat motif L(535)X3G(539)X2A(542)X3V(546)X2L(549) rather than through the alternative glycine zipper motif A(536)X3G(540)X3G(544) (typical for TMD dimerization in many proteins). To evaluate the significance of TMD interactions for full-length EphA2, we substituted key residues in the heptad repeat motif (HR variant: G539I, A542I, G553I) or in the glycine zipper motif (GZ variant: G540I, G544I) and expressed YFP-tagged EphA2 (WT, HR, and GZ variants) in HEK293T cells. Confocal microscopy revealed a similar distribution of all EphA2-YFP variants in cells. The expression of EphA2-YFP variants and their kinase activity (phosphorylation of Tyr(588) and/or Tyr(594)) and ephrin-A3 binding were analyzed with flow cytometry on a single cell basis. Activation of any EphA2 variant is found to occur even without ephrin stimulation when the EphA2 content in cells is sufficiently high. Ephrin-A3 binding is not affected in mutant variants. Mutations in the TMD have a significant effect on EphA2 activity. Both ligand-dependent and ligand-independent activities are enhanced for the HR variant and reduced for the GZ variant compared with the WT. These findings allow us to suggest TMD dimerization switching between the heptad repeat and glycine zipper motifs, corresponding to inactive and active receptor states, respectively, as a mechanism underlying EphA2 signal transduction.
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Affiliation(s)
- George V Sharonov
- From the Department of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of RAS, 117997 Moscow, Russia, the Faculty of Medicine, Moscow State University, 119992 Moscow, Russia
| | - Eduard V Bocharov
- From the Department of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of RAS, 117997 Moscow, Russia
| | - Peter M Kolosov
- the Department of Molecular Neurobiology, Institute of Higher Nervous Activity and Neurophysiology of RAS, 117485 Moscow, Russia, and
| | - Maria V Astapova
- From the Department of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of RAS, 117997 Moscow, Russia
| | - Alexander S Arseniev
- From the Department of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of RAS, 117997 Moscow, Russia
| | - Alexey V Feofanov
- From the Department of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of RAS, 117997 Moscow, Russia, the Biological Faculty, Moscow State University, 119992 Moscow, Russia
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5
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Barton WA, Dalton AC, Seegar TCM, Himanen JP, Nikolov DB. Tie2 and Eph receptor tyrosine kinase activation and signaling. Cold Spring Harb Perspect Biol 2014; 6:cshperspect.a009142. [PMID: 24478383 DOI: 10.1101/cshperspect.a009142] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The Eph and Tie cell surface receptors mediate a variety of signaling events during development and in the adult organism. As other receptor tyrosine kinases, they are activated on binding of extracellular ligands and their catalytic activity is tightly regulated on multiple levels. The Eph and Tie receptors display some unique characteristics, including the requirement of ligand-induced receptor clustering for efficient signaling. Interestingly, both Ephs and Ties can mediate different, even opposite, biological effects depending on the specific ligand eliciting the response and on the cellular context. Here we discuss the structural features of these receptors, their interactions with various ligands, as well as functional implications for downstream signaling initiation. The Eph/ephrin structures are already well reviewed and we only provide a brief overview on the initial binding events. We go into more detail discussing the Tie-angiopoietin structures and recognition.
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Affiliation(s)
- William A Barton
- Department of Biochemistry and Molecular Biology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298
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6
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Zhang L, Sodt AJ, Venable RM, Pastor RW, Buck M. Prediction, refinement, and persistency of transmembrane helix dimers in lipid bilayers using implicit and explicit solvent/lipid representations: microsecond molecular dynamics simulations of ErbB1/B2 and EphA1. Proteins 2012; 81:365-76. [PMID: 23042146 DOI: 10.1002/prot.24192] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/12/2012] [Accepted: 09/21/2012] [Indexed: 12/26/2022]
Abstract
All-atom simulations are carried out on ErbB1/B2 and EphA1 transmembrane helix dimers in lipid bilayers starting from their solution/DMPC bicelle NMR structures. Over the course of microsecond trajectories, the structures remain in close proximity to the initial configuration and satisfy the majority of experimental tertiary contact restraints. These results further validate CHARMM protein/lipid force fields and simulation protocols on Anton. Separately, dimer conformations are generated using replica exchange in conjunction with an implicit solvent and lipid representation. The implicit model requires further improvement, and this study investigates whether lengthy all-atom molecular dynamics simulations can alleviate the shortcomings of the initial conditions. The simulations correct many of the deficiencies. For example, excessive helix twisting is eliminated over a period of hundreds of nanoseconds. The helix tilt, crossing angles, and dimer contacts approximate those of the NMR-derived structure, although the detailed contact surface remains off-set for one of two helices in both systems. Hence, even microsecond simulations are not long enough for extensive helix rotations. The alternate structures can be rationalized with reference to interaction motifs and may represent still sought after receptor states that are important in ErbB1/B2 and EphA1 signaling.
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Affiliation(s)
- Liqun Zhang
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106, USA
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7
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Polyansky AA, Volynsky PE, Efremov RG. Structural, dynamic, and functional aspects of helix association in membranes: a computational view. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2012; 83:129-61. [PMID: 21570667 DOI: 10.1016/b978-0-12-381262-9.00004-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This review surveys recent achievements of molecular computer modeling in understanding spatial structure, dynamics, and mechanisms of functioning of transmembrane α-helical dimers in membranes. The factors driving self-association of hydrophobic helices in the membrane milieu are considered with examples of their applications to biologically relevant problems. The emphasis is made on the recent results, which help to understand important aspects of structure-function relations for these systems and their biological activity. Limitations and shortcomings of the methods, along with their perspectives in design of new membrane active agents, are discussed.
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Affiliation(s)
- Anton A Polyansky
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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8
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A photon-free approach to transmembrane protein structure determination. J Mol Biol 2011; 414:596-610. [PMID: 22024595 DOI: 10.1016/j.jmb.2011.10.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 10/04/2011] [Accepted: 10/11/2011] [Indexed: 02/05/2023]
Abstract
The structures of membrane proteins are generally solved using samples dissolved in micelles, bicelles, or occasionally phospholipid bilayers using X-ray diffraction or magnetic resonance. Because these are less than perfect mimics of true biological membranes, the structures are often confirmed by evaluating the effects of mutations on the properties of the protein in their native cellular environments. Low-resolution structures are also sometimes generated from the results of site-directed mutagenesis when other structural data are incomplete or not available. Here, we describe a rapid and automated approach to determine structures from data on site-directed mutants for the special case of homo-oligomeric helical bundles. The method uses as input an experimental profile of the effects of mutations on some property of the protein. This profile is then interpreted by assuming that positions that have large effects on structure/function when mutated project toward the center of the oligomeric bundle. Model bundles are generated, and correlation analysis is used to score which structures have inter-subunit C(β) distances between adjoining monomers that best correlate with the experimental profile. These structures are then clustered and refined using energy-based minimization methods. For a set of 10 homo-oligomeric TM protein structures ranging from dimers to pentamers, we show that our method predicts structures to within 1-2 Å backbone RMSD relative to X-ray and NMR structures. This level of agreement approaches the precision of NMR structures solved in different membrane mimetics.
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9
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Kalli A, Hall B, Campbell I, Sansom M. A helix heterodimer in a lipid bilayer: prediction of the structure of an integrin transmembrane domain via multiscale simulations. Structure 2011; 19:1477-84. [PMID: 22000516 PMCID: PMC3195670 DOI: 10.1016/j.str.2011.07.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Revised: 06/27/2011] [Accepted: 07/13/2011] [Indexed: 11/09/2022]
Abstract
Dimerization of transmembrane (TM) α helices of membrane receptors plays a key role in signaling. We show that molecular dynamics simulations yield models of integrin TM helix heterodimers, which agree well with available NMR structures. We use a multiscale simulation approach, combining coarse-grained and subsequent atomistic simulation, to model the dimerization of wild-type (WT) and mutated sequences of the αIIb and β3 integrin TM helices. The WT helices formed a stable, right-handed dimer with the same helix-helix interface as in the published NMR structure (PDB: 2K9J). In contrast, the presence of disruptive mutations perturbed the interface between the helices, altering the conformational stability of the dimer. The αIIb/β3 interface was more flexible than that of, e.g., glycophorin A. This is suggestive of a role for alternative packing modes of the TM helices in transbilayer signaling.
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Affiliation(s)
- Antreas C. Kalli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Benjamin A. Hall
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Iain D. Campbell
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mark S.P. Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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10
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Bocharov EV, Volynsky PE, Pavlov KV, Efremov RG, Arseniev AS. Structure elucidation of dimeric transmembrane domains of bitopic proteins. Cell Adh Migr 2010; 4:284-98. [PMID: 20421711 DOI: 10.4161/cam.4.2.11930] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The interaction between transmembrane helices is of great interest because it directly determines biological activity of a membrane protein. Either destroying or enhancing such interactions can result in many diseases related to dysfunction of different tissues in human body. One much studied form of membrane proteins known as bitopic protein is a dimer containing two membrane-spanning helices associating laterally. Establishing structure-function relationship as well as rational design of new types of drugs targeting membrane proteins requires precise structural information about this class of objects. At present time, to investigate spatial structure and internal dynamics of such transmembrane helical dimers, several strategies were developed based mainly on a combination of NMR spectroscopy, optical spectroscopy, protein engineering and molecular modeling. These approaches were successfully applied to homo- and heterodimeric transmembrane fragments of several bitopic proteins, which play important roles in normal and in pathological conditions of human organism.
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Affiliation(s)
- Eduard V Bocharov
- Division of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia.
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