1
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Mancinelli CD, Marx DC, Gonzalez-Hernandez AJ, Huynh K, Mancinelli L, Arefin A, Khelashvilli G, Levitz J, Eliezer D. Control of G protein-coupled receptor function via membrane-interacting intrinsically disordered C-terminal domains. Proc Natl Acad Sci U S A 2024; 121:e2407744121. [PMID: 38985766 PMCID: PMC11260148 DOI: 10.1073/pnas.2407744121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 06/07/2024] [Indexed: 07/12/2024] Open
Abstract
G protein-coupled receptors (GPCRs) control intracellular signaling cascades via agonist-dependent coupling to intracellular transducers including heterotrimeric G proteins, GPCR kinases (GRKs), and arrestins. In addition to their critical interactions with the transmembrane core of active GPCRs, all three classes of transducers have also been reported to interact with receptor C-terminal domains (CTDs). An underexplored aspect of GPCR CTDs is their possible role as lipid sensors given their proximity to the membrane. CTD-membrane interactions have the potential to control the accessibility of key regulatory CTD residues to downstream effectors and transducers. Here, we report that the CTDs of two closely related family C GPCRs, metabotropic glutamate receptor 2 (mGluR2) and mGluR3, bind to membranes and that this interaction can regulate receptor function. We first characterize CTD structure with NMR spectroscopy, revealing lipid composition-dependent modes of membrane binding. Using molecular dynamics simulations and structure-guided mutagenesis, we then identify key conserved residues and cancer-associated mutations that modulate CTD-membrane binding. Finally, we provide evidence that mGluR3 transducer coupling is controlled by CTD-membrane interactions in live cells, which may be subject to regulation by CTD phosphorylation and changes in membrane composition. This work reveals an additional mechanism of GPCR modulation, suggesting that CTD-membrane binding may be a general regulatory mode throughout the broad GPCR superfamily.
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Affiliation(s)
| | - Dagan C. Marx
- Department of Biochemistry, Weill Cornell Medicine, New York, NY10065
| | | | - Kevin Huynh
- Department of Biochemistry, Weill Cornell Medicine, New York, NY10065
| | - Lucia Mancinelli
- Department of Biochemistry, Weill Cornell Medicine, New York, NY10065
| | - Anisul Arefin
- Department of Biochemistry, Weill Cornell Medicine, New York, NY10065
| | - George Khelashvilli
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY10065
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY10065
- Department of Psychiatry, Weill Cornell Medicine, New York, NY10065
| | - David Eliezer
- Department of Biochemistry, Weill Cornell Medicine, New York, NY10065
- Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY10065
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2
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Chang YC, Cao Z, Chen WT, Huang WC. Effects of stand-alone polar residue on membrane protein stability and structure. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184325. [PMID: 38653423 DOI: 10.1016/j.bbamem.2024.184325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 04/11/2024] [Accepted: 04/17/2024] [Indexed: 04/25/2024]
Abstract
Helical membrane proteins generally have a hydrophobic nature, with apolar side chains comprising the majority of the transmembrane (TM) helices. However, whenever polar side chains are present in the TM domain, they often exert a crucial role in structural interactions with other polar residues, such as TM helix associations and oligomerization. Moreover, polar residues in the TM region also often participate in protein functions, such as the Schiff base bonding between Lys residues and retinal in rhodopsin-like membrane proteins. Although many studies have focused on these functional polar residues, our understanding of stand-alone polar residues that are energetically unfavored in TM helixes is limited. Here, we adopted bacteriorhodopsin (bR) as a model system and systematically mutated 17 of its apolar Leu or Phe residues to polar Asn. Stability measurements of the resulting mutants revealed that all of these polar substitutions reduced bR stability to various extents, and the extent of destabilization of each mutant bR is also correlated to different structural factors, such as the relative accessible surface area and membrane depth of the mutation site. Structural analyses of these Asn residues revealed that they form sidechain-to-backbone hydrogen bonds that alleviate the unfavorable energetics in hydrophobic and apolar surroundings. Our results indicate that membrane proteins are able to accommodate certain stand-alone polar residues in the TM region without disrupting overall structures.
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Affiliation(s)
- Yu-Chu Chang
- Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan; International Ph.D. Program for Cell Therapy and Regeneration Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
| | - Zheng Cao
- Department of Chemistry and Biochemistry, Molecular Biology Institute, UCLA, Los Angeles, CA 90095, United States of America
| | - Wai-Ting Chen
- Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Wei-Chun Huang
- Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
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3
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Mancinelli C, Marx DC, Gonzalez-Hernandez AJ, Huynh K, Mancinelli L, Arefin A, Khelashvilli G, Levitz J, Eliezer D. Control of G protein-coupled receptor function via membrane-interacting intrinsically disordered C-terminal domains. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.16.553551. [PMID: 37645938 PMCID: PMC10462050 DOI: 10.1101/2023.08.16.553551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
G protein-coupled receptors (GPCRs) control intracellular signaling cascades via agonist-dependent coupling to intracellular transducers including heterotrimeric G proteins, GPCR kinases (GRKs), and arrestins. In addition to their critical interactions with the transmembrane core of active GPCRs, all three classes of transducers have also been reported to interact with receptor C-terminal domains (CTDs). An underexplored aspect of GPCR CTDs is their possible role as lipid sensors given their proximity to the membrane. CTD-membrane interactions have the potential to control the accessibility of key regulatory CTD residues to downstream effectors and transducers. Here we report that the CTDs of two closely related family C GPCRs, metabotropic glutamate receptor 2 (mGluR2) and mGluR3, bind to membranes and that this interaction can regulate receptor function. We first characterize CTD structure with NMR spectroscopy, revealing lipid composition-dependent modes of membrane binding. Using molecular dynamics simulations and structure-guided mutagenesis, we then identify key conserved residues and cancer-associated mutations that modulate CTD-membrane binding. Finally, we provide evidence that mGluR3 transducer coupling is controlled by CTD-membrane interactions in live cells, which may be subject to regulation by CTD phosphorylation and changes in membrane composition. This work reveals a novel mechanism of GPCR modulation, suggesting that CTD-membrane binding may be a general regulatory mode throughout the broad GPCR superfamily.
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Affiliation(s)
- Chiara Mancinelli
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
- equal contribution
| | - Dagan C. Marx
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
- equal contribution
| | | | - Kevin Huynh
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | - Lucia Mancinelli
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | - Anisul Arefin
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
| | - George Khelashvilli
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY 10065, USA
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Psychiatry, Weill Cornell Medicine, New York, NY 10065, USA
| | - David Eliezer
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA
- Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY 10065, USA
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4
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Samanta R, Gray JJ. Implicit model to capture electrostatic features of membrane environment. PLoS Comput Biol 2024; 20:e1011296. [PMID: 38252688 PMCID: PMC10833867 DOI: 10.1371/journal.pcbi.1011296] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 02/01/2024] [Accepted: 12/13/2023] [Indexed: 01/24/2024] Open
Abstract
Membrane protein structure prediction and design are challenging due to the complexity of capturing the interactions in the lipid layer, such as those arising from electrostatics. Accurately capturing electrostatic energies in the low-dielectric membrane often requires expensive Poisson-Boltzmann calculations that are not scalable for membrane protein structure prediction and design. In this work, we have developed a fast-to-compute implicit energy function that considers the realistic characteristics of different lipid bilayers, making design calculations tractable. This method captures the impact of the lipid head group using a mean-field-based approach and uses a depth-dependent dielectric constant to characterize the membrane environment. This energy function Franklin2023 (F23) is built upon Franklin2019 (F19), which is based on experimentally derived hydrophobicity scales in the membrane bilayer. We evaluated the performance of F23 on five different tests probing (1) protein orientation in the bilayer, (2) stability, and (3) sequence recovery. Relative to F19, F23 has improved the calculation of the tilt angle of membrane proteins for 90% of WALP peptides, 15% of TM-peptides, and 25% of the adsorbed peptides. The performances for stability and design tests were equivalent for F19 and F23. The speed and calibration of the implicit model will help F23 access biophysical phenomena at long time and length scales and accelerate the membrane protein design pipeline.
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Affiliation(s)
- Rituparna Samanta
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jeffrey J. Gray
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- Program in Molecular Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America
- Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
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5
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Rout M, Mishra S, Panda S, Dehury B, Pati S. Lipid and cholesterols modulate the dynamics of SARS-CoV-2 viral ion channel ORF3a and its pathogenic variants. Int J Biol Macromol 2024; 254:127986. [PMID: 37944718 DOI: 10.1016/j.ijbiomac.2023.127986] [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: 08/24/2023] [Revised: 11/06/2023] [Accepted: 11/07/2023] [Indexed: 11/12/2023]
Abstract
SARS-CoV-2 accessory protein, ORF3a is a putative ion channel which immensely contributes to viral pathogenicity by modulating host immune responses and virus-host interactions. Relatively high expression of ORF3a in diseased individuals and implication with inflammasome activation, apoptosis and autophagy inhibition, ratifies as an effective target for developing vaccines and therapeutics. Herein, we present the elusive dynamics of ORF3a-dimeric state using all-atoms molecular dynamics (MD) simulations at μ-seconds scale in a heterogeneous lipid-mimetic system in multiple replicates. Additionally, we also explore the effect of non-synonymous pathogenic mutations on ORF3a ion channel activity and viral pathogenicity in different SARS-CoV-2 variants using various structure-based protein stability (ΔΔG) tools and computational saturation mutagenesis. Our study ascertains the role of phosphatidylcholines and cholesterol in modulating the structure of ORF3a, which perturbs the size and flexibility of the polar cavity that allows permeation of large cations. Discrete trend in ion channel pore radius and area per lipid arises the premise that presence of lipids might also affect the overall conformation of ORF3a. MD structural-ensembles, in some replicates rationalize the crucial role of TM2 in maintaining the native structure of ORF3a. We also infer that loss of structural stability primarily grounds for pathogenicity in more than half of the pathogenic variants of ORF3a. Overall, the effect of mutation on alteration of ion permeability of ORF3a, proposed in this study brings mechanistic insights into variant consequences on viral membrane proteins of SARS-CoV-2, which can be utilized for the development of novel therapeutics to treat COVID-19 and other coronavirus diseases.
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Affiliation(s)
- Madhusmita Rout
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Chandrasekharpur, Bhubaneswar 751023, Odisha, India
| | - Sarbani Mishra
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Chandrasekharpur, Bhubaneswar 751023, Odisha, India
| | - Sunita Panda
- Mycology Division, ICMR-Regional Medical Research Centre, Chandrasekharpur, Bhubaneswar 751023, Odisha, India
| | - Budheswar Dehury
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Chandrasekharpur, Bhubaneswar 751023, Odisha, India.
| | - Sanghamitra Pati
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Chandrasekharpur, Bhubaneswar 751023, Odisha, India.
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6
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Almeida PF. In Search of a Molecular View of Peptide-Lipid Interactions in Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 37478368 DOI: 10.1021/acs.langmuir.3c00538] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Lipid bilayer membranes are often represented as a continuous nonpolar slab with a certain thickness bounded by two more polar interfaces. Phenomena such as peptide binding to the membrane surface, folding, insertion, translocation, and diffusion are typically interpreted on the basis of this view. In this Perspective, I argue that this membrane representation as a hydrophobic continuum solvent is not adequate to understand peptide-lipid interactions. Lipids are not small compared to membrane-active peptides: their sizes are similar. Therefore, peptide diffusion needs to be understood in terms of free volume, not classical continuum mechanics; peptide solubility or partitioning in membranes cannot be interpreted in terms of hydrophobic mismatch between membrane thickness and peptide length; peptide folding and translocation, often involving cationic peptides, can only be understood if realizing that lipids adapt to the presence of peptides and the membrane may undergo considerable lipid redistribution in the process. In all of those instances, the detailed molecular interactions between the peptide residues and the lipid components are essential to understand the mechanisms involved.
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Affiliation(s)
- Paulo F Almeida
- Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, North Carolina 28403, United States
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7
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Samanta R, Gray JJ. Implicit model to capture electrostatic features of membrane environment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546486. [PMID: 37425950 PMCID: PMC10327106 DOI: 10.1101/2023.06.26.546486] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Membrane protein structure prediction and design are challenging due to the complexity of capturing the interactions in the lipid layer, such as those arising from electrostatics. Accurately capturing electrostatic energies in the low-dielectric membrane often requires expensive Poisson-Boltzmann calculations that are not scalable for membrane protein structure prediction and design. In this work, we have developed a fast-to-compute implicit energy function that considers the realistic characteristics of different lipid bilayers, making design calculations tractable. This method captures the impact of the lipid head group using a mean-field-based approach and uses a depth-dependent dielectric constant to characterize the membrane environment. This energy function Franklin2023 (F23) is built upon Franklin2019 (F19), which is based on experimentally derived hydrophobicity scales in the membrane bilayer. We evaluated the performance of F23 on five different tests probing (1) protein orientation in the bilayer, (2) stability, and (3) sequence recovery. Relative to F19, F23 has improved the calculation of the tilt angle of membrane proteins for 90% of WALP peptides, 15% of TM-peptides, and 25% of the adsorbed peptides. The performances for stability and design tests were equivalent for F19 and F23. The speed and calibration of the implicit model will help F23 access biophysical phenomena at long time and length scales and accelerate the membrane protein design pipeline.
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Affiliation(s)
- Rituparna Samanta
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jeffrey J Gray
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, United States
- Program in Molecular Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, United States
- Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland, United States
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8
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Tiemann JKS, Zschach H, Lindorff-Larsen K, Stein A. Interpreting the molecular mechanisms of disease variants in human transmembrane proteins. Biophys J 2023:S0006-3495(22)03941-8. [PMID: 36600598 DOI: 10.1016/j.bpj.2022.12.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 11/19/2022] [Accepted: 12/21/2022] [Indexed: 01/06/2023] Open
Abstract
Next-generation sequencing of human genomes reveals millions of missense variants, some of which may lead to loss of protein function and ultimately disease. Here, we investigate missense variants in membrane proteins-key drivers in cell signaling and recognition. We find enrichment of pathogenic variants in the transmembrane region across 19,000 functionally classified variants in human membrane proteins. To accurately predict variant consequences, one fundamentally needs to understand the underlying molecular processes. A key mechanism underlying pathogenicity in missense variants of soluble proteins has been shown to be loss of stability. Membrane proteins, however, are widely understudied. Here, we interpret variant effects on a larger scale by performing structure-based estimations of changes in thermodynamic stability using a membrane-specific energy function and analyses of sequence conservation during evolution of 15 transmembrane proteins. We find evidence for loss of stability being the cause of pathogenicity in more than half of the pathogenic variants, indicating that this is a driving factor also in membrane-protein-associated diseases. Our findings show how computational tools aid in gaining mechanistic insights into variant consequences for membrane proteins. To enable broader analyses of disease-related and population variants, we include variant mappings for the entire human proteome.
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Affiliation(s)
- Johanna Katarina Sofie Tiemann
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark; Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Henrike Zschach
- Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Kresten Lindorff-Larsen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | - Amelie Stein
- Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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9
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Mitchell W, Tamucci JD, Ng EL, Liu S, Birk AV, Szeto HH, May ER, Alexandrescu AT, Alder NN. Structure-activity relationships of mitochondria-targeted tetrapeptide pharmacological compounds. eLife 2022; 11:75531. [PMID: 35913044 PMCID: PMC9342957 DOI: 10.7554/elife.75531] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 07/03/2022] [Indexed: 11/13/2022] Open
Abstract
Mitochondria play a central role in metabolic homeostasis, and dysfunction of this organelle underpins the etiology of many heritable and aging-related diseases. Tetrapeptides with alternating cationic and aromatic residues such as SS-31 (elamipretide) show promise as therapeutic compounds for mitochondrial disorders. In this study, we conducted a quantitative structure-activity analysis of three alternative tetrapeptide analogs, benchmarked against SS-31, that differ with respect to aromatic side chain composition and sequence register. We present the first structural models for this class of compounds, obtained with Nuclear Magnetic Resonance (NMR) and molecular dynamics approaches, showing that all analogs except for SS-31 form compact reverse turn conformations in the membrane-bound state. All peptide analogs bound cardiolipin-containing membranes, yet they had significant differences in equilibrium binding behavior and membrane interactions. Notably, analogs had markedly different effects on membrane surface charge, supporting a mechanism in which modulation of membrane electrostatics is a key feature of their mechanism of action. The peptides had no strict requirement for side chain composition or sequence register to permeate cells and target mitochondria in mammalian cell culture assays. All four peptides were pharmacologically active in serum withdrawal cell stress models yet showed significant differences in their abilities to restore mitochondrial membrane potential, preserve ATP content, and promote cell survival. Within our peptide set, the analog containing tryptophan side chains, SPN10, had the strongest impact on most membrane properties and showed greatest efficacy in cell culture studies. Taken together, these results show that side chain composition and register influence the activity of these mitochondria-targeted peptides, helping provide a framework for the rational design of next-generation therapeutics with enhanced potency.
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Affiliation(s)
- Wayne Mitchell
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Jeffrey D Tamucci
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Emery L Ng
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Shaoyi Liu
- Social Profit Network, Menlo Park, CA, United States
| | - Alexander V Birk
- Department of Biology, York College of CUNY, New York, NY, United States
| | - Hazel H Szeto
- Social Profit Network, Menlo Park, CA, United States
| | - Eric R May
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Andrei T Alexandrescu
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, United States
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10
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Rujas E, Leaman DP, Insausti S, Carravilla P, García-Porras M, Largo E, Morillo I, Sánchez-Eugenia R, Zhang L, Cui H, Iloro I, Elortza F, Julien JP, Eggeling C, Zwick MB, Caaveiro JM, Nieva JL. Focal accumulation of aromaticity at the CDRH3 loop mitigates 4E10 polyreactivity without altering its HIV neutralization profile. iScience 2021; 24:102987. [PMID: 34505005 PMCID: PMC8413895 DOI: 10.1016/j.isci.2021.102987] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 07/08/2021] [Accepted: 08/12/2021] [Indexed: 11/29/2022] Open
Abstract
Broadly neutralizing antibodies (bnAbs) against HIV-1 are frequently associated with the presence of autoreactivity/polyreactivity, a property that can limit their use as therapeutic agents. The bnAb 4E10, targeting the conserved Membrane proximal external region (MPER) of HIV-1, displays almost pan-neutralizing activity across globally circulating HIV-1 strains but exhibits nonspecific off-target interactions with lipid membranes. The hydrophobic apex of the third complementarity-determining region of the heavy chain (CDRH3) loop, which is essential for viral neutralization, critically contributes to this detrimental effect. Here, we have replaced the aromatic/hydrophobic residues from the apex of the CDRH3 of 4E10 with a single aromatic molecule through chemical modification to generate a variant that preserves the neutralization potency and breadth of 4E10 but with reduced autoreactivity. Collectively, our study suggests that the localized accumulation of aromaticity by chemical modification provides a pathway to ameliorate the adverse effects triggered by the CDRH3 of anti-HIV-1 MPER bnAbs.
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Affiliation(s)
- Edurne Rujas
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Daniel P. Leaman
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Sara Insausti
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Pablo Carravilla
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
- Institute of Applied Optics and Biophysics Friedrich-Schiller-University Jena, Max-Wien Platz 1, 07743 Jena, Germany
- Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
| | - Miguel García-Porras
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Eneko Largo
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Izaskun Morillo
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Rubén Sánchez-Eugenia
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Lei Zhang
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Hong Cui
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Ibon Iloro
- Proteomics Platform, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), CIBERehd, ProteoRed-ISCIII, Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Félix Elortza
- Proteomics Platform, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), CIBERehd, ProteoRed-ISCIII, Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Jean-Philippe Julien
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
- Department of Immunology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Christian Eggeling
- Institute of Applied Optics and Biophysics Friedrich-Schiller-University Jena, Max-Wien Platz 1, 07743 Jena, Germany
- Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DS Oxford, UK
| | - Michael B. Zwick
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jose M.M. Caaveiro
- Laboratory of Global Healthcare, School of Pharmaceutical Sciences, Kyushu University, Fukuoka 819-0395, Japan
| | - José L. Nieva
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
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11
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Bolosov IA, Panteleev PV, Sychev SV, Sukhanov SV, Mironov PA, Myshkin MY, Shenkarev ZO, Ovchinnikova TV. Dodecapeptide Cathelicidins of Cetartiodactyla: Structure, Mechanism of Antimicrobial Action, and Synergistic Interaction With Other Cathelicidins. Front Microbiol 2021; 12:725526. [PMID: 34484167 PMCID: PMC8415029 DOI: 10.3389/fmicb.2021.725526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 07/19/2021] [Indexed: 12/02/2022] Open
Abstract
In this study, dodecapeptide cathelicidins were shown to be widespread antimicrobial peptides among the Cetruminantia clade. In particular, we investigated the dodecapeptide from the domestic goat Capra hircus, designated as ChDode and its unique ortholog from the sperm whale Physeter catodon (PcDode). ChDode contains two cysteine residues, while PcDode consists of two dodecapeptide building blocks and contains four cysteine residues. The recombinant analogs of the peptides were obtained by heterologous expression in Escherichia coli cells. The structures of the peptides were studied by circular dichroism (CD), FTIR, and NMR spectroscopy. It was demonstrated that PcDode adopts a β-hairpin structure in water and resembles β-hairpin antimicrobial peptides, while ChDode forms a β-structural antiparallel covalent dimer, stabilized by two intermonomer disulfide bonds. Both peptides reveal a significant right-handed twist about 200 degrees per 8 residues. In DPC micelles ChDode forms flat β-structural tetramers by antiparallel non-covalent association of the dimers. The tetramers incorporate into the micelles in transmembrane orientation. Incorporation into the micelles and dimerization significantly diminished the amplitude of backbone motions of ChDode at the picosecond-nanosecond timescale. When interacting with negatively charged membranes containing phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), the ChDode peptide adopted similar oligomeric structure and was capable to form ion-conducting pores without membrane lysis. Despite modest antibacterial activity of ChDode, a considerable synergistic effect of this peptide in combination with another goat cathelicidin – the α-helical peptide ChMAP-28 was observed. This effect is based on an increase in permeability of bacterial membranes. In turn, this mechanism can lead to an increase in the efficiency of the combined action of the synergistic pair ChMAP-28 with the Pro-rich peptide mini-ChBac7.5Nα targeting the bacterial ribosome.
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Affiliation(s)
- Ilia A Bolosov
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Pavel V Panteleev
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Phystech School of Biological and Medical Physics, Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia
| | - Sergei V Sychev
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Stanislav V Sukhanov
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Pavel A Mironov
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Mikhail Yu Myshkin
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Zakhar O Shenkarev
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Phystech School of Biological and Medical Physics, Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia
| | - Tatiana V Ovchinnikova
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Phystech School of Biological and Medical Physics, Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia.,Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
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12
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Tryptophan, an Amino-Acid Endowed with Unique Properties and Its Many Roles in Membrane Proteins. CRYSTALS 2021. [DOI: 10.3390/cryst11091032] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Tryptophan is an aromatic amino acid with unique physico-chemical properties. It is often encountered in membrane proteins, especially at the level of the water/bilayer interface. It plays a role in membrane protein stabilization, anchoring and orientation in lipid bilayers. It has a hydrophobic character but can also engage in many types of interactions, such as π–cation or hydrogen bonds. In this review, we give an overview of the role of tryptophan in membrane proteins and a more detailed description of the underlying noncovalent interactions it can engage in with membrane partners.
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13
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Alford RF, Samanta R, Gray JJ. Diverse Scientific Benchmarks for Implicit Membrane Energy Functions. J Chem Theory Comput 2021; 17:5248-5261. [PMID: 34310137 DOI: 10.1021/acs.jctc.0c00646] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Energy functions are fundamental to biomolecular modeling. Their success depends on robust physical formalisms, efficient optimization, and high-resolution data for training and validation. Over the past 20 years, progress in each area has advanced soluble protein energy functions. Yet, energy functions for membrane proteins lag behind due to sparse and low-quality data, leading to overfit tools. To overcome this challenge, we assembled a suite of 12 tests on independent data sets varying in size, diversity, and resolution. The tests probe an energy function's ability to capture membrane protein orientation, stability, sequence, and structure. Here, we present the tests and use the franklin2019 energy function to demonstrate them. We then identify areas for energy function improvement and discuss potential future integration with machine-learning-based optimization methods. The tests are available through the Rosetta Benchmark Server (https://benchmark.graylab.jhu.edu/) and GitHub (https://github.com/rfalford12/Implicit-Membrane-Energy-Function-Benchmark).
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Affiliation(s)
- Rebecca F Alford
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States
| | - Rituparna Samanta
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States
| | - Jeffrey J Gray
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, United States.,Program in Molecular Biophysics, Johns Hopkins University, Baltimore, Maryland, United States
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14
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Marx DC, Fleming KG. Membrane proteins enter the fold. Curr Opin Struct Biol 2021; 69:124-130. [PMID: 33975156 DOI: 10.1016/j.sbi.2021.03.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 03/15/2021] [Accepted: 03/21/2021] [Indexed: 11/19/2022]
Abstract
Membrane proteins have historically been recalcitrant to biophysical folding studies. However, recent adaptations of methods from the soluble protein folding field have found success in their applications to transmembrane proteins composed of both α-helical and β-barrel conformations. Avoiding aggregation is critical for the success of these experiments. Altogether these studies are leading to discoveries of folding trajectories, foundational stabilizing forces and better-defined endpoints that enable more accurate interpretation of thermodynamic data. Increased information on membrane protein folding in the cell shows that the emerging biophysical principles are largely recapitulated even in the complex biological environment.
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Affiliation(s)
- Dagan C Marx
- TC Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD, 21218, United States
| | - Karen G Fleming
- TC Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD, 21218, United States.
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15
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Characterization of the Features of Water Inside the SecY Translocon. J Membr Biol 2021; 254:133-139. [PMID: 33811496 DOI: 10.1007/s00232-021-00178-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 03/23/2021] [Indexed: 10/21/2022]
Abstract
Despite extended experimental and computational studies, the mechanism regulating membrane protein folding and stability in cell membranes is not fully understood. In this review, I will provide a personal and partial account of the scientific efforts undertaken by Dr. Stephen White to shed light on this topic. After briefly describing the role of water and the hydrophobic effect on cellular processes, I will discuss the physical chemistry of water confined inside the SecY translocon pore. I conclude with a review of recent literature that attempts to answer fundamental questions on the pathway and energetics of translocon-guided membrane protein insertion.
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16
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Marx DC, Fleming KG. Local Bilayer Hydrophobicity Modulates Membrane Protein Stability. J Am Chem Soc 2021; 143:764-772. [DOI: 10.1021/jacs.0c09412] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Dagan C. Marx
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Karen G. Fleming
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, United States
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17
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Mena EL, Jevtić P, Greber BJ, Gee CL, Lew BG, Akopian D, Nogales E, Kuriyan J, Rape M. Structural basis for dimerization quality control. Nature 2020; 586:452-456. [PMID: 32814905 PMCID: PMC8024055 DOI: 10.1038/s41586-020-2636-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 05/21/2020] [Indexed: 12/21/2022]
Abstract
Most quality control pathways target misfolded proteins to prevent toxic aggregation and neurodegeneration 1. Dimerization quality control (DQC) further improves proteostasis by eliminating complexes of aberrant composition 2, yet how it detects incorrect subunits is still unknown. Here, we provide structural insight into target selection by SCFFBXL17, a DQC E3 ligase that ubiquitylates and helps degrade inactive heterodimers of BTB proteins, while sparing functional homodimers. We find that SCFFBXL17 disrupts aberrant BTB dimers that fail to stabilize an intermolecular β-sheet around a highly divergent β-strand of the BTB domain. Complex dissociation allows SCFFBXL17 to wrap around a single BTB domain for robust ubiquitylation. SCFFBXL17 therefore probes both shape and complementarity of BTB domains, a mechanism that is well suited to establish quality control of complex composition for recurrent interaction modules.
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Affiliation(s)
- Elijah L Mena
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Predrag Jevtić
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Basil J Greber
- California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, USA.,Molecular Biophysics and Integrative Bio-Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Christine L Gee
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Brandon G Lew
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA
| | - David Akopian
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Eva Nogales
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA.,California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, USA.,Molecular Biophysics and Integrative Bio-Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - John Kuriyan
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA.,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA.,California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, USA.,Molecular Biophysics and Integrative Bio-Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Department of Chemistry, University of California at Berkeley, Berkeley, CA, USA
| | - Michael Rape
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA. .,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, USA. .,California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, USA.
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18
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Rujas E, Insausti S, Leaman DP, Carravilla P, González-Resines S, Monceaux V, Sánchez-Eugenia R, García-Porras M, Iloro I, Zhang L, Elortza F, Julien JP, Saéz-Cirión A, Zwick MB, Eggeling C, Ojida A, Domene C, Caaveiro JMM, Nieva JL. Affinity for the Interface Underpins Potency of Antibodies Operating In Membrane Environments. Cell Rep 2020; 32:108037. [PMID: 32814041 PMCID: PMC7861656 DOI: 10.1016/j.celrep.2020.108037] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/02/2020] [Accepted: 07/23/2020] [Indexed: 11/29/2022] Open
Abstract
The contribution of membrane interfacial interactions to recognition of membrane-embedded antigens by antibodies is currently unclear. This report demonstrates the optimization of this type of antibodies via chemical modification of regions near the membrane but not directly involved in the recognition of the epitope. Using the HIV-1 antibody 10E8 as a model, linear and polycyclic synthetic aromatic compounds are introduced at selected sites. Molecular dynamics simulations predict the favorable interactions of these synthetic compounds with the viral lipid membrane, where the epitope of the HIV-1 glycoprotein Env is located. Chemical modification of 10E8 with aromatic acetamides facilitates the productive and specific recognition of the native antigen, partially buried in the crowded environment of the viral membrane, resulting in a dramatic increase of its capacity to block viral infection. These observations support the harnessing of interfacial affinity through site-selective chemical modification to optimize the function of antibodies that target membrane-proximal epitopes.
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Affiliation(s)
- Edurne Rujas
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain; Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Sara Insausti
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain
| | - Daniel P Leaman
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Pablo Carravilla
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain; Institute of Applied Optics and Biophysics Friedrich-Schiller-University Jena, Max-Wien Platz 4, 07743 Jena, Germany; Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
| | | | - Valérie Monceaux
- Institut Pasteur, Unité HIV Inflammation et Persistance, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Rubén Sánchez-Eugenia
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain
| | - Miguel García-Porras
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain
| | - Ibon Iloro
- Proteomics Platform, CIC bioGUNE, Parque Tecnológico de Vizcaya, 48160 Derio, Spain
| | - Lei Zhang
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Félix Elortza
- Proteomics Platform, CIC bioGUNE, Parque Tecnológico de Vizcaya, 48160 Derio, Spain
| | - Jean-Philippe Julien
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Immunology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Asier Saéz-Cirión
- Institut Pasteur, Unité HIV Inflammation et Persistance, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Michael B Zwick
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Christian Eggeling
- Institute of Applied Optics and Biophysics Friedrich-Schiller-University Jena, Max-Wien Platz 4, 07743 Jena, Germany; Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
| | - Akio Ojida
- Department of Chemical Biology, School of Pharmaceutical Sciences, Kyushu University, Fukuoka 819-0395, Japan
| | - Carmen Domene
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AX, UK; Department of Chemistry, University of Oxford, Oxford OX1 3TF, UK
| | - Jose M M Caaveiro
- Laboratory of Global Health Care, School of Pharmaceutical Sciences, Kyushu University, Fukuoka 819-0395, Japan.
| | - José L Nieva
- Instituto Biofisika (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080 Bilbao, Spain.
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19
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Horne JE, Brockwell DJ, Radford SE. Role of the lipid bilayer in outer membrane protein folding in Gram-negative bacteria. J Biol Chem 2020; 295:10340-10367. [PMID: 32499369 PMCID: PMC7383365 DOI: 10.1074/jbc.rev120.011473] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
β-Barrel outer membrane proteins (OMPs) represent the major proteinaceous component of the outer membrane (OM) of Gram-negative bacteria. These proteins perform key roles in cell structure and morphology, nutrient acquisition, colonization and invasion, and protection against external toxic threats such as antibiotics. To become functional, OMPs must fold and insert into a crowded and asymmetric OM that lacks much freely accessible lipid. This feat is accomplished in the absence of an external energy source and is thought to be driven by the high thermodynamic stability of folded OMPs in the OM. With such a stable fold, the challenge that bacteria face in assembling OMPs into the OM is how to overcome the initial energy barrier of membrane insertion. In this review, we highlight the roles of the lipid environment and the OM in modulating the OMP-folding landscape and discuss the factors that guide folding in vitro and in vivo We particularly focus on the composition, architecture, and physical properties of the OM and how an understanding of the folding properties of OMPs in vitro can help explain the challenges they encounter during folding in vivo Current models of OMP biogenesis in the cellular environment are still in flux, but the stakes for improving the accuracy of these models are high. OMP folding is an essential process in all Gram-negative bacteria, and considering the looming crisis of widespread microbial drug resistance it is an attractive target. To bring down this vital OMP-supported barrier to antibiotics, we must first understand how bacterial cells build it.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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20
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Lessen HJ, Majumdar A, Fleming KG. Backbone Hydrogen Bond Energies in Membrane Proteins Are Insensitive to Large Changes in Local Water Concentration. J Am Chem Soc 2020; 142:6227-6235. [PMID: 32134659 PMCID: PMC7610216 DOI: 10.1021/jacs.0c00290] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A hallmark feature of biological lipid bilayer structure is a depth-dependent polarity gradient largely resulting from the change in water concentration over the angstrom length scale. This gradient is particularly steep as it crosses the membrane interfacial regions where the water concentration drops at least a million-fold along the direction of the bilayer normal. Although local water content is often assumed to be a major determinant of membrane protein stability, the effect of the water-induced polarity gradient upon backbone hydrogen bond strength has not been systematically investigated. We addressed this question by measuring the free energy change for a number of backbone hydrogen bonds in the transmembrane protein OmpW. These values were obtained at 33 backbone amides from hydrogen/deuterium fractionation factors by nuclear magnetic resonance spectroscopy. We surprisingly found that OmpW backbone hydrogen bond energies do not vary over a wide range of water concentrations that are characteristic of the solvation environment in the bilayer interfacial region. We validated the interpretation of our results by determining the hydrodynamic and solvation properties of our OmpW-micelle complex using analytical ultracentrifugation and molecular dynamics simulations. The magnitudes of the backbone hydrogen bond free energy changes in our study are comparable to those observed in water-soluble proteins, the H-segment of the leader peptidase helix used in the von Heijne and White biological scale experiments, and several interfacial peptides. Our results agree with those reported for the transmembrane α-helical portion of the amyloid precursor protein after the latter values were adjusted for kinetic isotope effects. Overall, our work suggests that backbone hydrogen bonds provide modest thermodynamic stability to membrane protein structures and that many amides are unaffected by dehydration within the bilayer.
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Affiliation(s)
- Henry J Lessen
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Ananya Majumdar
- The Johns Hopkins University Biomolecular NMR Center, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Karen G Fleming
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, United States
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21
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Protein Structure Prediction and Design in a Biologically Realistic Implicit Membrane. Biophys J 2020; 118:2042-2055. [PMID: 32224301 DOI: 10.1016/j.bpj.2020.03.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 02/04/2020] [Accepted: 03/09/2020] [Indexed: 11/19/2022] Open
Abstract
Protein design is a powerful tool for elucidating mechanisms of function and engineering new therapeutics and nanotechnologies. Although soluble protein design has advanced, membrane protein design remains challenging because of difficulties in modeling the lipid bilayer. In this work, we developed an implicit approach that captures the anisotropic structure, shape of water-filled pores, and nanoscale dimensions of membranes with different lipid compositions. The model improves performance in computational benchmarks against experimental targets, including prediction of protein orientations in the bilayer, ΔΔG calculations, native structure discrimination, and native sequence recovery. When applied to de novo protein design, this approach designs sequences with an amino acid distribution near the native amino acid distribution in membrane proteins, overcoming a critical flaw in previous membrane models that were prone to generating leucine-rich designs. Furthermore, the proteins designed in the new membrane model exhibit native-like features including interfacial aromatic side chains, hydrophobic lengths compatible with bilayer thickness, and polar pores. Our method advances high-resolution membrane protein structure prediction and design toward tackling key biological questions and engineering challenges.
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22
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Gupta A, Mahalakshmi R. Reversible folding energetics of Yersinia Ail barrel reveals a hyperfluorescent intermediate. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183097. [PMID: 31672545 DOI: 10.1016/j.bbamem.2019.183097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 10/01/2019] [Accepted: 10/10/2019] [Indexed: 12/17/2022]
Abstract
Deducing the molecular details of membrane protein folding has lately become an important area of research in biology. Using Ail, an outer membrane protein (OMP) from Yersina pestis as our model, we explore details of β-barrel folding, stability, and unfolding. Ail displays a simple transmembrane β-barrel topology. Here, we find that Ail follows a simple two-state mechanism in its folding and unfolding thermodynamics. Interestingly, Ail displays multi-step folding kinetics. The early kinetic intermediates in the folding pathway populate near the unfolded state (βT ≈ 0.20), and do not display detectable changes in the local environment of the two interface indoles. Interestingly, tryptophans regulate the late events of barrel rearrangement, and Ail thermodynamic stability. We show that W149 → Y/F/A substitution destabilizes Ail by ~0.13-1.7 kcal mol-1, but retains path-independent thermodynamic equilibrium of Ail. In surprising contrast, substituting W42 and retaining W149 shifts the thermodynamic equilibrium to an apparent kinetic retardation of only the unfolding process, which gives rise to an associated increase in scaffold stability by ~0.3-1.1 kcal mol-1. This is accompanied by the formation of an unusual hyperfluorescent state in the unfolding pathway that is more structured, and represents a conformationally dynamic unfolding intermediate with the interface W149 now lipid solvated. The defined role of each tryptophan and poorer folding efficiency of Trp mutants together presents compelling evidence for the importance of interface aromatics in the unique (un)folding pathway of Ail, and offers interesting insight on alternative pathways in generalized OMP assembly and unfolding mechanisms.
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Affiliation(s)
- Ankit Gupta
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal 462066. India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal 462066. India.
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23
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Waheed Q, Khan HM, He T, Roberts M, Gershenson A, Reuter N. Interfacial Aromatics Mediating Cation-π Interactions with Choline-Containing Lipids Can Contribute as Much to Peripheral Protein Affinity for Membranes as Aromatics Inserted below the Phosphates. J Phys Chem Lett 2019; 10:3972-3977. [PMID: 31246477 DOI: 10.1021/acs.jpclett.9b01639] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Membrane-binding interfaces of peripheral proteins are restricted to a small part of their exposed surface, so the ability to engage in strong selective interactions with membrane lipids at various depths in the interface, both below and above the phosphates, is an advantage. Driven by their hydrophobicity, aromatic amino acids preferentially partition into membrane interfaces, often below the phosphates, yet enthalpically favorable interactions with the lipid headgroups, above the phosphate plane, are likely to further stabilize high interfacial positions. Using free-energy perturbation, we calculate the energetic cost of alanine substitution for 11 interfacial aromatic amino acids from 3 peripheral proteins. We show that the involvement in cation-π interactions with the headgroups (i) increases the ΔΔGtransfer as compared with insertion at the same depth without cation-π stabilization and (ii) can contribute at least as much as deeper insertion below the phosphates, highlighting the multiple roles of aromatics in peripheral membrane protein affinity.
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Affiliation(s)
- Qaiser Waheed
- Department of Biological Sciences , University of Bergen , N-5020 Bergen , Norway
- Computational Biology Unit, Department of Informatics , University of Bergen , N-5020 Bergen , Norway
| | - Hanif M Khan
- Department of Biological Sciences , University of Bergen , N-5020 Bergen , Norway
- Computational Biology Unit, Department of Informatics , University of Bergen , N-5020 Bergen , Norway
| | - Tao He
- Department of Chemistry , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Mary Roberts
- Department of Chemistry , Boston College , Chestnut Hill , Massachusetts 02467 , United States
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology , University of Massachusetts Amherst , Amherst , Massachusetts 01003 , United States
- Molecular and Cellular Biology Graduate Program , University of Massachusetts Amherst , Amherst , Massachusetts 01003 , United States
| | - Nathalie Reuter
- Computational Biology Unit, Department of Informatics , University of Bergen , N-5020 Bergen , Norway
- Department of Chemistry , University of Bergen , N-5020 Bergen , Norway
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24
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Iyer BR, Mahalakshmi R. Hydrophobic Characteristic Is Energetically Preferred for Cysteine in a Model Membrane Protein. Biophys J 2019; 117:25-35. [PMID: 31221440 PMCID: PMC6626846 DOI: 10.1016/j.bpj.2019.05.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 05/17/2019] [Accepted: 05/22/2019] [Indexed: 11/17/2022] Open
Abstract
The naturally occurring amino acid cysteine has often been implicated with a crucial role in maintaining protein structure and stability. An intriguing duality in the intrinsic hydrophobicity of the cysteine side chain is that it exhibits both polar as well as hydrophobic characteristics. Here, we have utilized a cysteine-scanning mutational strategy on the transmembrane β-barrel PagP to examine the membrane depth-dependent energetic contribution of the free cysteine side chain (thiolate) versus the parent residue at an experimental pH of 9.5 in phosphatidylcholine vesicles. We find that introduction of cysteine causes destabilization at several of the 26 lipid-facing sites of PagP that we mutated in this study. The destabilization is minimal (0.5-1.5 kcal/mol) when the mutation is toward the bilayer midplane, whereas it is higher in magnitude (3.0-5.0 kcal/mol) near the bilayer interface. These observations suggest that cysteine forms more favorable interactions with the hydrophobic lipid core as compared to the amphiphilic water-lipid interface. The destabilizing effect is more pronounced when cysteine replaces the interfacial aromatics, which are known to participate in tertiary interaction networks in transmembrane β-barrels. Our observations from experiments involving the introduction of cysteine at the bilayer midplane further strengthen previous views that the free cysteine side chain does possess strongly apolar characteristics. Additionally, the free energy changes observed upon cysteine incorporation show a depth-dependent correlation with the estimated energetic cost of partitioning derived from reported hydrophobicity scales. Our results and observations from the thermodynamic analysis of the PagP barrel may explain why cysteine, despite possessing a polar sulfhydryl group, tends to behave as a hydrophobic (rather than polar) residue in folded protein structures.
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Affiliation(s)
- Bharat Ramasubramanian Iyer
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh, India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh, India.
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25
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Marinko J, Huang H, Penn WD, Capra JA, Schlebach JP, Sanders CR. Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis. Chem Rev 2019; 119:5537-5606. [PMID: 30608666 PMCID: PMC6506414 DOI: 10.1021/acs.chemrev.8b00532] [Citation(s) in RCA: 162] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Indexed: 12/13/2022]
Abstract
Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.
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Affiliation(s)
- Justin
T. Marinko
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Hui Huang
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Wesley D. Penn
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - John A. Capra
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37245, United States
| | - Jonathan P. Schlebach
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Charles R. Sanders
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
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26
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Roushar FJ, Gruenhagen TC, Penn WD, Li B, Meiler J, Jastrzebska B, Schlebach JP. Contribution of Cotranslational Folding Defects to Membrane Protein Homeostasis. J Am Chem Soc 2018; 141:204-215. [PMID: 30537820 DOI: 10.1021/jacs.8b08243] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Membrane proteins are prone to misfolding and degradation within the cell, yet the nature of the conformational defects involved in this process remain poorly understood. The earliest stages of membrane protein folding are mediated by the Sec61 translocon, a molecular machine that facilitates the lateral partitioning of the polypeptide into the membrane. Proper membrane integration is an essential prerequisite for folding of the nascent chain. However, the marginal energetic drivers of this reaction suggest the translocon may operate with modest fidelity. In this work, we employed biophysical modeling in conjunction with quantitative biochemical measurements in order to evaluate the extent to which cotranslational folding defects influence membrane protein homeostasis. Protein engineering was employed to selectively perturb the topological energetics of human rhodopsin, and the expression and cellular trafficking of engineered variants were quantitatively compared. Our results reveal clear relationships between topological energetics and the efficiency of rhodopsin biogenesis, which appears to be limited by the propensity of a polar transmembrane domain to achieve its correct topological orientation. Though the polarity of this segment is functionally constrained, we find that its topology can be stabilized in a manner that enhances biogenesis without compromising the functional properties of rhodopsin. Furthermore, sequence alignments reveal this topological instability has been conserved throughout the course of evolution. These results suggest that topological defects significantly contribute to the inefficiency of membrane protein folding in the cell. Additionally, our findings suggest that the marginal stability of rhodopsin may represent an evolved trait.
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Affiliation(s)
- Francis J Roushar
- Department of Chemistry , Indiana University , Bloomington , Indiana 47405 , United States
| | - Timothy C Gruenhagen
- Department of Chemistry , Indiana University , Bloomington , Indiana 47405 , United States
| | - Wesley D Penn
- Department of Chemistry , Indiana University , Bloomington , Indiana 47405 , United States
| | - Bian Li
- Department of Chemistry , Vanderbilt University , Nashville , Tennessee 37235 , United States
| | - Jens Meiler
- Department of Chemistry , Vanderbilt University , Nashville , Tennessee 37235 , United States
| | - Beata Jastrzebska
- Department of Pharmacology , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Jonathan P Schlebach
- Department of Chemistry , Indiana University , Bloomington , Indiana 47405 , United States
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27
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Roberts MF, Khan HM, Goldstein R, Reuter N, Gershenson A. Search and Subvert: Minimalist Bacterial Phosphatidylinositol-Specific Phospholipase C Enzymes. Chem Rev 2018; 118:8435-8473. [DOI: 10.1021/acs.chemrev.8b00208] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Mary F. Roberts
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | | | - Rebecca Goldstein
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | | | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
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28
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29
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Cao Z, Bian Y, Hu G, Zhao L, Kong Z, Yang Y, Wang J, Zhou Y. Bias-Exchange Metadynamics Simulation of Membrane Permeation of 20 Amino Acids. Int J Mol Sci 2018; 19:E885. [PMID: 29547563 PMCID: PMC5877746 DOI: 10.3390/ijms19030885] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 03/11/2018] [Accepted: 03/12/2018] [Indexed: 11/16/2022] Open
Abstract
Thermodynamics of the permeation of amino acids from water to lipid bilayers is an important first step for understanding the mechanism of cell-permeating peptides and the thermodynamics of membrane protein structure and stability. In this work, we employed bias-exchange metadynamics simulations to simulate the membrane permeation of all 20 amino acids from water to the center of a dipalmitoylphosphatidylcholine (DPPC) membrane (consists of 256 lipids) by using both directional and torsion angles for conformational sampling. The overall accuracy for the free energy profiles obtained is supported by significant correlation coefficients (correlation coefficient at 0.5-0.6) between our results and previous experimental or computational studies. The free energy profiles indicated that (1) polar amino acids have larger free energy barriers than nonpolar amino acids; (2) negatively charged amino acids are the most difficult to enter into the membrane; and (3) conformational transitions for many amino acids during membrane crossing is the key for reduced free energy barriers. These results represent the first set of simulated free energy profiles of membrane crossing for all 20 amino acids.
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Affiliation(s)
- Zanxia Cao
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
- College of Physics and Electronic Information, Dezhou University, Dezhou 253023, China.
| | - Yunqiang Bian
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
| | - Guodong Hu
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
- College of Physics and Electronic Information, Dezhou University, Dezhou 253023, China.
| | - Liling Zhao
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
- College of Physics and Electronic Information, Dezhou University, Dezhou 253023, China.
| | - Zhenzhen Kong
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
- College of Life Science, Shandong Normal University, Jinan 250014, China.
| | - Yuedong Yang
- Institute for Glycomics and School of Information and Communication Technology, Griffith University, Parklands Dr, Southport, QLD 4222, Australia.
- School of Data and Computer Science, Sun Yat-sen University, Guangzhou 510275, China.
| | - Jihua Wang
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
- College of Physics and Electronic Information, Dezhou University, Dezhou 253023, China.
| | - Yaoqi Zhou
- Shandong Provincial Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China.
- Institute for Glycomics and School of Information and Communication Technology, Griffith University, Parklands Dr, Southport, QLD 4222, Australia.
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30
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Koehler Leman J, Bonneau R, Ulmschneider MB. Statistically derived asymmetric membrane potentials from α-helical and β-barrel membrane proteins. Sci Rep 2018. [PMID: 29535329 PMCID: PMC5849751 DOI: 10.1038/s41598-018-22476-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Modeling membrane protein (MP) folding, insertion, association and their interactions with other proteins, lipids, and drugs requires accurate transfer free energies (TFEs). Various TFE scales have been derived to quantify the energy required or released to insert an amino acid or protein into the membrane. Experimental measurement of TFEs is challenging, and only few scales were extended to depth-dependent energetic profiles. Statistical approaches can be used to derive such potentials; however, this requires a sufficient number of MP structures. Furthermore, MPs are tightly coupled to bilayers that are heterogeneous in terms of lipid composition, asymmetry, and protein content between organisms and organelles. Here we derived asymmetric implicit membrane potentials from β-barrel and α-helical MPs and use them to predict topology, depth and orientation of proteins in the membrane. Our data confirm the ‘charge-outside’ and ‘positive-inside’ rules for β-barrels and α-helical proteins, respectively. We find that the β-barrel profiles have greater asymmetry than the ones from α-helical proteins, as a result of the different membrane architecture of gram-negative bacterial outer membranes and the existence of lipopolysaccharide in the outer leaflet. Our data further suggest that pore-facing residues in β-barrels have a larger contribution to membrane insertion and stability than previously suggested.
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Affiliation(s)
- Julia Koehler Leman
- Center for Computational Biology, Flatiron Institute, Simons Foundation, New York, 10010 NY, USA. .,Department of Biology, Center for Genomics and Systems Biology, New York University, New York, 10003 NY, USA.
| | - Richard Bonneau
- Center for Computational Biology, Flatiron Institute, Simons Foundation, New York, 10010 NY, USA.,Department of Biology, Center for Genomics and Systems Biology, New York University, New York, 10003 NY, USA.,Department of Computer Science, New York University, New York, 10012 NY, USA
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31
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Situ AJ, Kang SM, Frey BB, An W, Kim C, Ulmer TS. Membrane Anchoring of α-Helical Proteins: Role of Tryptophan. J Phys Chem B 2018; 122:1185-1194. [PMID: 29323921 PMCID: PMC11025564 DOI: 10.1021/acs.jpcb.7b11227] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The function of membrane proteins relies on a defined orientation of protein relative to lipid. In apparent correlation to protein anchoring, tryptophan residues are enriched in the lipid headgroup region. To characterize the thermodynamic and structural basis of this relationship in α-helical membrane proteins, we examined the role of three conserved tryptophans in the folding of the heterodimeric integrin αIIbβ3 transmembrane (TM) complex in phospholipid bicelles and mammalian membranes. In the homogenous lipid environment of bicelles, tryptophan was replaceable by residues of distinct polarities. The appropriate polarity was guided by the electrostatic potential of the tryptophan surrounding, suggesting that tryptophan can complement diverse environments by adjusting the orientation of its anisotropic side chain to achieve site-specific anchoring. As a sole membrane anchor, tryptophan made a contribution of 0.4 kcal/mol to TM complex stability in bicelles. In membranes, it proved more difficult to replace tryptophan even by tyrosine, indicating a superior capacity to interact with heterogeneous lipids of biological membranes. Interestingly, at intracellular TM helix ends, where integrin activation is initiated, sequence motifs that interact with lipids via opposing polarity patterns were found to restrict TM helix orientations beyond tryptophan anchoring. In contrast to bicelles, phenylalanine became the least accepted substitute in membranes, demonstrating an increased role of the hydrophobic effect. Altogether, our study implicates a wide amphiphilic range of tryptophan, membrane complexity, and the hydrophobic effect to be important factors in tryptophan membrane anchoring.
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Affiliation(s)
- Alan J Situ
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - So-Min Kang
- Department of Life Sciences, Korea University , 145 Anam-Ro, Seongbuk-Gu, Seoul 136-701, South Korea
| | - Benjamin B Frey
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Woojin An
- Department of Biochemistry & Molecular Medicine and Norris Comprehensive Cancer Center, University of Southern California , Los Angeles, California 90033, United States
| | - Chungho Kim
- Department of Life Sciences, Korea University , 145 Anam-Ro, Seongbuk-Gu, Seoul 136-701, South Korea
| | - Tobias S Ulmer
- Department of Biochemistry & Molecular Medicine and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , 1501 San Pablo Street, Los Angeles, California 90033, United States
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32
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Schiffrin B, Brockwell DJ, Radford SE. Outer membrane protein folding from an energy landscape perspective. BMC Biol 2017; 15:123. [PMID: 29268734 PMCID: PMC5740924 DOI: 10.1186/s12915-017-0464-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The cell envelope is essential for the survival of Gram-negative bacteria. This specialised membrane is densely packed with outer membrane proteins (OMPs), which perform a variety of functions. How OMPs fold into this crowded environment remains an open question. Here, we review current knowledge about OMP folding mechanisms in vitro and discuss how the need to fold to a stable native state has shaped their folding energy landscapes. We also highlight the role of chaperones and the β-barrel assembly machinery (BAM) in assisting OMP folding in vivo and discuss proposed mechanisms by which this fascinating machinery may catalyse OMP folding.
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Affiliation(s)
- Bob Schiffrin
- Astbury Centre for Structural Molecular Biology, School of Molecular and 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 and 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 and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
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33
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Chaturvedi D, Mahalakshmi R. Position-Specific contribution of interface tryptophans on membrane protein energetics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:451-457. [PMID: 29128310 DOI: 10.1016/j.bbamem.2017.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 10/11/2017] [Accepted: 11/07/2017] [Indexed: 02/06/2023]
Abstract
Interface tryptophans are key residues that facilitate the folding and stability of membrane proteins. Escherichia coli OmpX possesses two unique interface tryptophans, namely Trp76, which is present at the interface and is solvent-exposed, and Trp140, which is relatively more lipid solvated than Trp76 in symmetric lipid membranes. Here, we address the requirement for tryptophan and the consequences of aromatic amino acid substitutions on the folding and stability of OmpX. Using spectroscopic measurements of OmpX-Trp/Tyr/Phe mutants, we show that the specific mutation W76→Y allows barrel assembly >1.5-fold faster than native OmpX, and increases stability by ~0.4kcalmol-1. In contrast, mutating W140→F/Y lowers OmpX thermodynamic stability by ~0.4kcalmol-1, without affecting the folding kinetics. We conclude that the stabilizing effect of tryptophan at the membrane interface can be position-and local environment-specific. We propose that the thermodynamic contributions for interface residues be interpreted with caution.
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Affiliation(s)
- Deepti Chaturvedi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal 462066, India.
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34
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Marx DC, Fleming KG. Influence of Protein Scaffold on Side-Chain Transfer Free Energies. Biophys J 2017; 113:597-604. [PMID: 28793214 DOI: 10.1016/j.bpj.2017.06.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 06/15/2017] [Accepted: 06/19/2017] [Indexed: 11/26/2022] Open
Abstract
The process by which membrane proteins fold involves the burial of side chains into lipid bilayers. Both structure and function of membrane proteins depend on the magnitudes of side-chain transfer free energies (ΔΔGsco). In the absence of other interactions, ΔΔGsco is an independent property describing the energetics of an isolated side chain in the bilayer. However, in reality, side chains are attached to the peptide backbone and surrounded by other side chains in the protein scaffold in biology, which may alter the apparent ΔΔGsco. Previously we reported a whole protein water-to-bilayer hydrophobicity scale using the transmembrane β-barrel Escherichia coli OmpLA as a scaffold protein. To investigate how a different protein scaffold can modulate these energies, we measured ΔΔGsco for all 20 amino acids using the transmembrane β-barrel E. coli PagP as a scaffold protein. This study represents, to our knowledge, the first instance of ΔΔGsco measured in the same experimental conditions in two structurally and sequentially distinct protein scaffolds. Although the two hydrophobicity scales are strongly linearly correlated, we find that there are apparent scaffold induced changes in ΔΔGsco for more than half of the side chains, most of which are polar residues. We propose that the protein scaffold affects the ΔΔGsco of side chains that are buried in unfavorable environments by dictating the mechanisms by which the side chain can reach a more favorable environment and thus modulating the magnitude of ΔΔGsco.
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35
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Shen C, Xue M, Qiu H, Guo W. Insertion of Neurotransmitters into a Lipid Bilayer Membrane and Its Implication on Membrane Stability: A Molecular Dynamics Study. Chemphyschem 2017; 18:626-633. [PMID: 28054433 DOI: 10.1002/cphc.201601184] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 12/13/2016] [Indexed: 12/29/2022]
Abstract
The signaling molecules in neurons, called neurotransmitters, play an essential role in the transportation of neural signals, during which the neurotransmitters interact with not only specific receptors, but also cytomembranes, such as synaptic vesicle membranes and postsynaptic membranes. Through extensive molecular dynamics simulations, the atomic-scale insertion dynamics of typical neurotransmitters, including methionine enkephalin (ME), leucine enkephalin (LE), dopamine (DA), acetylcholine (ACh), and aspartic acid (ASP), into lipid bilayers is investigated. The results show that the first three neurotransmitters (ME, LE, and DA) are able to diffuse freely into both 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) membranes, and are guided by the aromatic residues Tyr and Phe. Only a limited number of these neurotransmitters are allowed to penetrate into the membrane, which suggests an intrinsic mechanism by which the membrane is protected from being destroyed by excessive inserted neurotransmitters. After spontaneous insertion, the neurotransmitters disturb the surrounding phospholipids in the membrane, as indicated by the altered distribution of components in lipid leaflets and the disordered lipid tails. In contrast, the last two neurotransmitters (ACh and ASP) cannot enter the membrane, but instead always diffuse freely in solution. These findings provide an understanding at the atomic level of how neurotransmitters interact with the surrounding cytomembrane, as well as their impact on membrane behavior.
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Affiliation(s)
- Chun Shen
- State Key Laboratory of Mechanics and Control of Mechanical Structure and Key Laboratory for Intelligent Nano Materials and Devices of the, Ministry of Education, and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, P.R. China
| | - Minmin Xue
- State Key Laboratory of Mechanics and Control of Mechanical Structure and Key Laboratory for Intelligent Nano Materials and Devices of the, Ministry of Education, and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, P.R. China
| | - Hu Qiu
- State Key Laboratory of Mechanics and Control of Mechanical Structure and Key Laboratory for Intelligent Nano Materials and Devices of the, Ministry of Education, and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, P.R. China
| | - Wanlin Guo
- State Key Laboratory of Mechanics and Control of Mechanical Structure and Key Laboratory for Intelligent Nano Materials and Devices of the, Ministry of Education, and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, P.R. China
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36
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Rujas E, Caaveiro JMM, Partida-Hanon A, Gulzar N, Morante K, Apellániz B, García-Porras M, Bruix M, Tsumoto K, Scott JK, Jiménez MÁ, Nieva JL. Structural basis for broad neutralization of HIV-1 through the molecular recognition of 10E8 helical epitope at the membrane interface. Sci Rep 2016; 6:38177. [PMID: 27905530 PMCID: PMC5131266 DOI: 10.1038/srep38177] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 11/04/2016] [Indexed: 12/13/2022] Open
Abstract
The mechanism by which the HIV-1 MPER epitope is recognized by the potent neutralizing antibody 10E8 at membrane interfaces remains poorly understood. To solve this problem, we have optimized a 10E8 peptide epitope and analyzed the structure and binding activities of the antibody in membrane and membrane-like environments. The X-ray crystal structure of the Fab-peptide complex in detergents revealed for the first time that the epitope of 10E8 comprises a continuous helix spanning the gp41 MPER/transmembrane domain junction (MPER-N-TMD; Env residues 671–687). The MPER-N-TMD helix projects beyond the tip of the heavy-chain complementarity determining region 3 loop, indicating that the antibody sits parallel to the plane of the membrane in binding the native epitope. Biophysical, biochemical and mutational analyses demonstrated that strengthening the affinity of 10E8 for the TMD helix in a membrane environment, correlated with its neutralizing potency. Our research clarifies the molecular mechanisms underlying broad neutralization of HIV-1 by 10E8, and the structure of its natural epitope. The conclusions of our research will guide future vaccine-design strategies targeting MPER.
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Affiliation(s)
- Edurne Rujas
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain.,Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Jose M M Caaveiro
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.,Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Angélica Partida-Hanon
- Institute of Physical Chemistry "Rocasolano" (IQFR-CSIC), Serrano 119, E-28006 Madrid, Spain
| | - Naveed Gulzar
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
| | - Koldo Morante
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.,Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Beatriz Apellániz
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
| | - Miguel García-Porras
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
| | - Marta Bruix
- Institute of Physical Chemistry "Rocasolano" (IQFR-CSIC), Serrano 119, E-28006 Madrid, Spain
| | - Kouhei Tsumoto
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.,Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Jamie K Scott
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada.,Faculty of Health Sciences, Simon Fraser University, Burnaby, Canada
| | - M Ángeles Jiménez
- Institute of Physical Chemistry "Rocasolano" (IQFR-CSIC), Serrano 119, E-28006 Madrid, Spain
| | - José L Nieva
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
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McDonald SK, Fleming KG. Negative Charge Neutralization in the Loops and Turns of Outer Membrane Phospholipase A Impacts Folding Hysteresis at Neutral pH. Biochemistry 2016; 55:6133-6137. [PMID: 27731977 DOI: 10.1021/acs.biochem.6b00652] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Hysteresis in equilibrium protein folding titrations is an experimental barrier that must be overcome to extract meaningful thermodynamic quantities. Traditional approaches to solving this problem involve testing a spectrum of solution conditions to find ones that achieve path independence. Through this procedure, a specific pH of 3.8 was required to achieve path independence for the water-to-bilayer equilibrium folding of outer membrane protein OmpLA. We hypothesized that the neutralization of negatively charged side chains (Asp and Glu) at pH 3.8 could be the physical basis for path-independent folding at this pH. To test this idea, we engineered variants of OmpLA with Asp → Asn and Glu → Gln mutations to neutralize the negative charges within various regions of the protein and tested for reversible folding at neutral pH. Although not fully resolved, our results show that these mutations in the periplasmic turns and extracellular loops are responsible for 60% of the hysteresis in wild-type folding. Overall, our study suggests that negative charges impact the folding hysteresis in outer membrane proteins and their neutralization may aid in protein engineering applications.
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Affiliation(s)
- Sarah K McDonald
- T. C. Jenkins Department of Biophysics, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Karen G Fleming
- T. C. Jenkins Department of Biophysics, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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Maurya SR, Mahalakshmi R. Control of human VDAC-2 scaffold dynamics by interfacial tryptophans is position specific. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2993-3004. [PMID: 27641490 PMCID: PMC5091009 DOI: 10.1016/j.bbamem.2016.09.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 09/09/2016] [Accepted: 09/13/2016] [Indexed: 12/05/2022]
Abstract
Membrane proteins employ specific distribution patterns of amino acids in their tertiary structure for adaptation to their unique bilayer environment. The solvent-bilayer interface, in particular, displays the characteristic ‘aromatic belt’ that defines the transmembrane region of the protein, and satisfies the amphipathic interfacial environment. Tryptophan—the key residue of this aromatic belt—is known to influence the folding efficiency and stability of a large number of well-studied α-helical and β-barrel membrane proteins. Here, we have used functional and biophysical techniques coupled with simulations, to decipher the contribution of strategically placed four intrinsic tryptophans of the human outer mitochondrial membrane protein, voltage-dependent anion channel isoform-2 (VDAC-2). We show that tryptophans help in maintaining the structural and functional integrity of folded hVDAC-2 barrel in micellar environments. The voltage gating characteristics of hVDAC-2 are affected upon mutation of tryptophans at positions 75, 86 and 221. We observe that Trp-160 and Trp-221 play a crucial role in the folding pathway of the barrel, and once folded, Trp-221 helps stabilize the folded protein in concert with Trp-75 and Trp-160. We further demonstrate that substituting Trp-86 with phenylalanine leads to the formation of stable barrel. We find that the region comprising strand β4 (Trp-86) and β10-14 (Trp-160 and Trp-221) display slower and faster folding kinetics, respectively, providing insight into a possible directional folding of hVDAC-2 from the C-terminus to N-terminus. Our results show that residue selection in a protein during evolution is a balancing compromise between optimum stability, function, and regulating protein turnover inside the cell. Aromatic belt of membrane proteins has key stabilization role. Human voltage-dependent anion channel isoform-2 (hVDAC-2) has four interfacial indoles. Tryptophans act in concert to drive folding and stabilization of the barrel. The 86th position shows preference for phenylalanine due to its buried environment. Strands β10–14 promote barrel folding and stabilize hVDAC-2.
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Affiliation(s)
- Svetlana Rajkumar Maurya
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India.
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