1
|
Gamage YI, Wadumesthri Y, Gutiérrez HR, Voronine DV, Pan J. The impact of transmembrane peptides on lipid bilayer structure and mechanics: A study of the transmembrane domain of the influenza A virus M2 protein. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184373. [PMID: 39047857 DOI: 10.1016/j.bbamem.2024.184373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/15/2024] [Accepted: 07/16/2024] [Indexed: 07/27/2024]
Abstract
Transmembrane peptides play important roles in many biological processes by interacting with lipid membranes. This study investigates how the transmembrane domain of the influenza A virus M2 protein, M2TM, affects the structure and mechanics of model lipid bilayers. Atomic force microscopy (AFM) imaging revealed small decreases in bilayer thickness with increasing peptide concentrations. AFM-based force spectroscopy experiments complemented by theoretical model analysis demonstrated significant decreases in bilayer's Young's modulus (E) and lateral area compressibility modulus (KA). This suggests that M2TM disrupts the cohesive interactions between neighboring lipid molecules, leading to a decrease in both the bilayer's resistance to indentation (E) and its ability to resist lateral compression/expansion (KA). The large decreases in bilayer elastic parameters (i.e., E and KA) contrast with small changes in bilayer thickness, implying that bilayer mechanics are not solely dictated by bilayer thickness in the presence of transmembrane peptides. The observed significant reduction in bilayer mechanical properties suggests a softening effect on the bilayer, potentially facilitating membrane curvature generation, a crucial step for M2-mediated viral budding. In parallel, our Raman spectroscopy revealed small but statistically significant changes in hydrocarbon chain vibrational dynamics, indicative of minor disordering in lipid chain conformation. Our findings provide useful insights into the complex interplay between transmembrane peptides and lipid bilayers, highlighting the significance of peptide-lipid interactions in modulating membrane structure, mechanics, and molecular dynamics.
Collapse
Affiliation(s)
| | - Yasinthara Wadumesthri
- Department of Physics, University of South Florida, Tampa, FL 33620, United States of America
| | | | - Dmitri V Voronine
- Department of Physics, University of South Florida, Tampa, FL 33620, United States of America
| | - Jianjun Pan
- Department of Physics, University of South Florida, Tampa, FL 33620, United States of America.
| |
Collapse
|
2
|
Sanders G, Borbat PP, Georgieva ER. Conformations of influenza A M2 protein in DOPC/DOPS and E. coli native lipids and proteins. Biophys J 2024:S0006-3495(24)00432-6. [PMID: 38932458 DOI: 10.1016/j.bpj.2024.06.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 04/21/2024] [Accepted: 06/24/2024] [Indexed: 06/28/2024] Open
Abstract
We compared the conformations of the transmembrane domain (TMD) of influenza A M2 (IM2) protein reconstituted in 1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPC/DOPS) bilayers to those in isolated Escherichia coli (E. coli) membranes, having preserved its native proteins and lipids. IM2 is a single-pass transmembrane protein known to assemble into a homo-tetrameric proton channel. To represent this channel, we made a construct containing the IM2's TMD region flanked by the juxtamembrane residues. The single cysteine substitution, L43C, of leucine located in the bilayer polar region was paramagnetically tagged with a methanethiosulfonate nitroxide label for the electron spin resonance (ESR) study. For this particular residue, we probed the conformations of the spin-labeled IM2 reconstituted in DOPC/DOPS and isolated E. coli membranes using continuous-wave ESR and double electron-electron resonance (DEER) spectroscopy. The total protein-to-lipid molar ratio spanned the range from 1:230 to 1:10,400. The continuous-wave ESR spectra corresponded to very slow spin-label motion in both environments. In all cases, the DEER data were reconstructed into distance distributions with well-resolved peaks at 1.68 and 2.37 nm in distance and amplitude ratios of 1.41 ± 0.2 and 2:1, respectively. This suggests four nitroxide spin labels located at the corners of a square, indicative of an axially symmetric tetramer. The distance modeling of DEER data with molecular modeling software applied to the NMR molecular structures (PDB: 2L0J) confirmed the symmetry and closed state of the C-terminal exit pore of the IM2 TMD tetramer in agreement with the model. Thus, we can conclude that, under conditions of pH 7.4 used in this study, IM2 TMD has similar conformations in model lipid bilayers and membranes made of native E. coli lipids and proteins of comparable thickness and fluidity, notwithstanding the complexity of the E. coli membranes caused by their lipid diversity and the abundance of integral and peripheral membrane proteins.
Collapse
Affiliation(s)
- Griffin Sanders
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, ACERT, Cornell University, Ithaca, New York
| | - Elka R Georgieva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas.
| |
Collapse
|
3
|
Carter T, Iqbal M. The Influenza A Virus Replication Cycle: A Comprehensive Review. Viruses 2024; 16:316. [PMID: 38400091 PMCID: PMC10892522 DOI: 10.3390/v16020316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 02/15/2024] [Accepted: 02/17/2024] [Indexed: 02/25/2024] Open
Abstract
Influenza A virus (IAV) is the primary causative agent of influenza, colloquially called the flu. Each year, it infects up to a billion people, resulting in hundreds of thousands of human deaths, and causes devastating avian outbreaks with worldwide losses worth billions of dollars. Always present is the possibility that a highly pathogenic novel subtype capable of direct human-to-human transmission will spill over into humans, causing a pandemic as devastating if not more so than the 1918 influenza pandemic. While antiviral drugs for influenza do exist, they target very few aspects of IAV replication and risk becoming obsolete due to antiviral resistance. Antivirals targeting other areas of IAV replication are needed to overcome this resistance and combat the yearly epidemics, which exact a serious toll worldwide. This review aims to summarise the key steps in the IAV replication cycle, along with highlighting areas of research that need more focus.
Collapse
Affiliation(s)
- Toby Carter
- The Pirbright Institute, Ash Road, Pirbright, Woking GU24 0NF, UK;
| | | |
Collapse
|
4
|
Townsend JA, Fapohunda O, Wang Z, Pham H, Taylor MT, Kloss B, Ho Park S, Opella S, Aspinwall CA, Marty MT. Differences in Oligomerization of the SARS-CoV-2 Envelope Protein, Poliovirus VP4, and HIV Vpu. Biochemistry 2024; 63:241-250. [PMID: 38216552 PMCID: PMC10872257 DOI: 10.1021/acs.biochem.3c00437] [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] [Indexed: 01/14/2024]
Abstract
Viroporins constitute a class of viral membrane proteins with diverse roles in the viral life cycle. They can self-assemble and form pores within the bilayer that transport substrates, such as ions and genetic material, that are critical to the viral infection cycle. However, there is little known about the oligomeric state of most viroporins. Here, we use native mass spectrometry in detergent micelles to uncover the patterns of oligomerization of the full-length SARS-CoV-2 envelope (E) protein, poliovirus VP4, and HIV Vpu. Our data suggest that the E protein is a specific dimer, VP4 is exclusively monomeric, and Vpu assembles into a polydisperse mixture of oligomers under these conditions. Overall, these results revealed the diversity in the oligomerization of viroporins, which has implications for the mechanisms of their biological functions as well as their potential as therapeutic targets.
Collapse
Affiliation(s)
- Julia A. Townsend
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Oluwaseun Fapohunda
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Zhihan Wang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Hieu Pham
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael T. Taylor
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Brian Kloss
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, New York, NY 10027, USA
| | - Sang Ho Park
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stanley Opella
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Craig A. Aspinwall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T. Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
| |
Collapse
|
5
|
Sanders G, Borbat PP, Georgieva ER. A comparative study of influenza A M2 protein conformations in DOPC/DOPS liposomes and in native E. coli membranes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.08.574681. [PMID: 38260371 PMCID: PMC10802500 DOI: 10.1101/2024.01.08.574681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
We compared the conformations of the transmembrane domain (TMD) of influenza A M2 (IAM2) protein reconstituted at pH 7.4 in DOPC/DOPS bilayers to those in isolated E. coli membranes, having preserved its native proteins and lipids. IAM2 is a single-pass transmembrane protein known to assemble into homo-tetrameric proton channel. To represent this channel, we made a construct containing the IAM2's TMD region flanked by the juxtamembrane residues. The single cysteine substitute, L43C, of leucine located in the bilayer polar region was paramagnetically tagged with a methanethiosulfonate nitroxide label for the ESR (electron spin resonance) study. We compared the conformations of the spin-labeled IAM2 residing in DOPC/DOPS and native E. coli membranes using continuous-wave (CW) ESR and double electron-electron resonance (DEER) spectroscopy. The total protein-to-lipid molar ratio spanned the range from 1:230 to 1:10,400⩦ The CW ESR spectra corresponded to a nearly rigid limit spin label dynamics in both environments. In all cases, the DEER data were reconstructed into the distance distributions showing well-resolved peaks at 1.68 nm and 2.37 nm. The peak distance ratio was 1.41±0.2 and the amplitude ratio was 2:1. This is what one expects from four nitroxide spin-labels located at the corners of a square, indicative of an axially symmetric tetramer. Distance modeling of DEER data with molecular modeling software applied to the NMR molecular structures (PDB: 2L0J) confirmed the symmetry and closed state of the C-terminal exit pore of the IAM2 tetramer in agreement with the NMR model. Thus, we can conclude that IAM2 TMD has similar conformations in model and native E. coli membranes of comparable thickness and fluidity, notwithstanding the complexity of the E. coli membranes caused by their lipid diversity and the abundance of integral and peripheral membrane proteins.
Collapse
Affiliation(s)
- Griffin Sanders
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409
| | - Peter P. Borbat
- Department of Chemistry and Chemical Biology and ACERT, Cornell University, Ithaca NY 14853
| | - Elka R. Georgieva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409
| |
Collapse
|
6
|
Petrich A, Chiantia S. Influenza A Virus Infection Alters Lipid Packing and Surface Electrostatic Potential of the Host Plasma Membrane. Viruses 2023; 15:1830. [PMID: 37766238 PMCID: PMC10537794 DOI: 10.3390/v15091830] [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: 08/07/2023] [Revised: 08/24/2023] [Accepted: 08/25/2023] [Indexed: 09/29/2023] Open
Abstract
The pathogenesis of influenza A viruses (IAVs) is influenced by several factors, including IAV strain origin and reassortment, tissue tropism and host type. While such factors were mostly investigated in the context of virus entry, fusion and replication, little is known about the viral-induced changes to the host lipid membranes which might be relevant in the context of virion assembly. In this work, we applied several biophysical fluorescence microscope techniques (i.e., Förster energy resonance transfer, generalized polarization imaging and scanning fluorescence correlation spectroscopy) to quantify the effect of infection by two IAV strains of different origin on the plasma membrane (PM) of avian and human cell lines. We found that IAV infection affects the membrane charge of the inner leaflet of the PM. Moreover, we showed that IAV infection impacts lipid-lipid interactions by decreasing membrane fluidity and increasing lipid packing. Because of such alterations, diffusive dynamics of membrane-associated proteins are hindered. Taken together, our results indicate that the infection of avian and human cell lines with IAV strains of different origins had similar effects on the biophysical properties of the PM.
Collapse
Affiliation(s)
| | - Salvatore Chiantia
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476 Potsdam, Germany
| |
Collapse
|
7
|
Townsend JA, Fapohunda O, Wang Z, Pham H, Taylor MT, Kloss B, Park SH, Opella S, Aspinwall CA, Marty MT. Differences in Oligomerization of the SARS-CoV-2 Envelope Protein, Poliovirus VP4, and HIV Vpu. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.18.553902. [PMID: 37645758 PMCID: PMC10462163 DOI: 10.1101/2023.08.18.553902] [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
Viroporins constitute a class of viral membrane proteins with diverse roles in the viral life cycle. They can self-assemble and form pores within the bilayer that transport substrates, such as ions and genetic material, that are critical to the viral infection cycle. However, there is little known about the oligomeric state of most viroporins. Here, we use native mass spectrometry (MS) in detergent micelles to uncover the patterns of oligomerization of the full-length SARS-CoV-2 envelope (E) protein, poliovirus VP4, and HIV Vpu. Our data suggest that the E protein is a specific dimer, VP4 is exclusively monomeric, and Vpu assembles into a polydisperse mixture of oligomers under these conditions. Overall, these results revealed the diversity in the oligomerization of viroporins, which has implications for mechanisms of their biological functions as well as their potential as therapeutic targets.
Collapse
Affiliation(s)
- Julia A. Townsend
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Oluwaseun Fapohunda
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Zhihan Wang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Hieu Pham
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael T. Taylor
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Brian Kloss
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, New York, NY 10027, USA
| | - Sang Ho Park
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stanley Opella
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Craig A. Aspinwall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T. Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
| |
Collapse
|
8
|
Kumar U, Goyal P, Madni ZK, Kamble K, Gaur V, Rajala MS, Salunke DM. A structure and knowledge-based combinatorial approach to engineering universal scFv antibodies against influenza M2 protein. J Biomed Sci 2023; 30:56. [PMID: 37491224 PMCID: PMC10367348 DOI: 10.1186/s12929-023-00950-2] [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: 04/26/2023] [Accepted: 07/03/2023] [Indexed: 07/27/2023] Open
Abstract
BACKGROUND The influenza virus enters the host via hemagglutinin protein binding to cell surface sialic acid. Receptor-mediated endocytosis is followed by viral nucleocapsid uncoating for replication aided by the transmembrane viral M2 proton ion channel. M2 ectodomain (M2e) is a potential universal candidate for monoclonal antibody therapy owing to its conserved nature across influenza virus subtypes and its importance in viral propagation. METHODS The phage-displayed naive human antibody libraries were screened against the short stretch of the N-terminal 10-mer peptide (SLLTEVETPI) of the M2e. ELISA, BLI, and flow cytometry assays were used to examine scFv binding to M2e epitopes. The scFv crystal structures were determined to examine the nature of the interactions. The potencies of the scFvs against the influenza virus were demonstrated by real-time PCR and confocal microscopy imaging. RESULTS The four unique scFv clones were obtained from the scFv phage-display antibody libraries and shown to exhibit binding with the 10-mer conserved part of the M2e and with full-length M2 protein expressed on the HEK293T cells. The crystal structure of scFv AU1 with M2e peptide showed the peptide as a dimer in the parallel beta-sheet conformation bound at the interface of two scFv CDRs. The scFv AU1 significantly restricted the release of H1N1 virus progeny from the infected A549 cells. CONCLUSION This structural and biochemical study showcased the binding of antibody scFv molecules with M2e peptide dimer, providing the structural insights for the function effect in terms of recognizing and restricting the release of new viral particles from an infected host cell.
Collapse
Affiliation(s)
- Ujjwal Kumar
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Priya Goyal
- Jawaharlal Nehru University, New Delhi, Delhi, 110067, India
| | - Zaid K Madni
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Kajal Kamble
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Vineet Gaur
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | | | - Dinakar M Salunke
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
| |
Collapse
|
9
|
Wort JL, Ackermann K, Giannoulis A, Bode BE. Enhanced sensitivity for pulse dipolar EPR spectroscopy using variable-time RIDME. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 352:107460. [PMID: 37167826 DOI: 10.1016/j.jmr.2023.107460] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 04/03/2023] [Accepted: 04/19/2023] [Indexed: 05/13/2023]
Abstract
Pulse dipolar EPR spectroscopy (PDS) measurements are an important complementary tool in structural biology and are increasingly applied to macromolecular assemblies implicated in human health and disease at physiological concentrations. This requires ever higher sensitivity, and recent advances have driven PDS measurements into the mid-nanomolar concentration regime, though optimization and acquisition of such measurements remains experimentally demanding and time expensive. One important consideration is that constant-time acquisition represents a hard limit for measurement sensitivity, depending on the maximum measured distance. Determining this distance a priori has been facilitated by machine-learning structure prediction (AlphaFold2 and RoseTTAFold) but is often confounded by non-representative behaviour in frozen solution that may mandate multiple rounds of optimization and acquisition. Herein, we endeavour to simultaneously enhance sensitivity and streamline PDS measurement optimization to one-step by benchmarking a variable-time acquisition RIDME experiment applied to CuII-nitroxide and CuII-CuII model systems. Results demonstrate marked sensitivity improvements of both 5- and 6-pulse variable-time RIDME of between 2- and 5-fold over the constant-time analogues.
Collapse
Affiliation(s)
- Joshua L Wort
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Scotland
| | - Katrin Ackermann
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Scotland
| | - Angeliki Giannoulis
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Scotland
| | - Bela E Bode
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Scotland.
| |
Collapse
|
10
|
Choi YM, Ajjaji D, Fleming KD, Borbat PP, Jenkins ML, Moeller BE, Fernando S, Bhatia SR, Freed JH, Burke JE, Thiam AR, Airola MV. Structural insights into perilipin 3 membrane association in response to diacylglycerol accumulation. Nat Commun 2023; 14:3204. [PMID: 37268630 PMCID: PMC10238389 DOI: 10.1038/s41467-023-38725-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 05/12/2023] [Indexed: 06/04/2023] Open
Abstract
Lipid droplets (LDs) are dynamic organelles that contain an oil core mainly composed of triglycerides (TAG) that is surrounded by a phospholipid monolayer and LD-associated proteins called perilipins (PLINs). During LD biogenesis, perilipin 3 (PLIN3) is recruited to nascent LDs as they emerge from the endoplasmic reticulum. Here, we analyze how lipid composition affects PLIN3 recruitment to membrane bilayers and LDs, and the structural changes that occur upon membrane binding. We find that the TAG precursors phosphatidic acid and diacylglycerol (DAG) recruit PLIN3 to membrane bilayers and define an expanded Perilipin-ADRP-Tip47 (PAT) domain that preferentially binds DAG-enriched membranes. Membrane binding induces a disorder to order transition of alpha helices within the PAT domain and 11-mer repeats, with intramolecular distance measurements consistent with the expanded PAT domain adopting a folded but dynamic structure upon membrane binding. In cells, PLIN3 is recruited to DAG-enriched ER membranes, and this requires both the PAT domain and 11-mer repeats. This provides molecular details of PLIN3 recruitment to nascent LDs and identifies a function of the PAT domain of PLIN3 in DAG binding.
Collapse
Affiliation(s)
- Yong Mi Choi
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Dalila Ajjaji
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Kaelin D Fleming
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8N 1A1, Canada
| | - Peter P Borbat
- National Biomedical Resource for Advanced Electron Spin Resonance Technology (ACERT), Cornell University, Ithaca, NY, 14853, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8N 1A1, Canada
| | - Brandon E Moeller
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8N 1A1, Canada
| | - Shaveen Fernando
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Surita R Bhatia
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Jack H Freed
- National Biomedical Resource for Advanced Electron Spin Resonance Technology (ACERT), Cornell University, Ithaca, NY, 14853, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8N 1A1, Canada.
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France.
| | - Michael V Airola
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, 11794, USA.
| |
Collapse
|
11
|
Kyaw A, Roepke K, Arthur T, Howard KP. Conformation of influenza AM2 membrane protein in nanodiscs and liposomes. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184152. [PMID: 36948480 PMCID: PMC10175228 DOI: 10.1016/j.bbamem.2023.184152] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/15/2023] [Accepted: 03/14/2023] [Indexed: 03/24/2023]
Abstract
The influenza A M2 protein (AM2) is a multifunctional membrane-associated homotetramer that orchestrates several essential events in the viral infection cycle including viral assembly and budding. An atomic-level conformational understanding of this key player in the influenza life cycle could inform new antiviral strategies. For conformational studies of complex systems like the AM2 membrane protein, a multipronged approach using different biophysical methods and different model membranes is a powerful way to incorporate complementary data and achieve a fuller, more robust understanding of the system. However, one must be aware of how the sample composition required for a particular method impacts the data collected and how conclusions are drawn. In that spirit, we systematically compared the properties of AM2 in two different model membranes: nanodiscs and liposomes. Electron paramagnetic spectroscopy of spin-labeled AM2 showed that the conformation and dynamics were strikingly similar in both AM2-nanodiscs and AM2-liposomes consistent with similar conformations in both model membranes. Analysis of spin labeled lipids embedded in both model membranes revealed that the bilayer in AM2-liposomes was more fluid and permeable to oxygen than AM2-nanodiscs with the same lipid composition. Once the difference in the partitioning of the paramagnetic oxygen relaxation agent was taken into account, the membrane topology of AM2 appeared to be the same in both liposomes and nanodiscs. Finally, functionally relevant AM2 conformational shifts previously seen in liposomes due to the addition of cholesterol were also observed in nanodiscs.
Collapse
Affiliation(s)
- Aye Kyaw
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Kyra Roepke
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Tyrique Arthur
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Kathleen P Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America.
| |
Collapse
|
12
|
Galazzo L, Bordignon E. Electron paramagnetic resonance spectroscopy in structural-dynamic studies of large protein complexes. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2023; 134-135:1-19. [PMID: 37321755 DOI: 10.1016/j.pnmrs.2022.11.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 11/11/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
Macromolecular protein assemblies are of fundamental importance for many processes inside the cell, as they perform complex functions and constitute central hubs where reactions occur. Generally, these assemblies undergo large conformational changes and cycle through different states that ultimately are connected to specific functions further regulated by additional small ligands or proteins. Unveiling the 3D structural details of these assemblies at atomic resolution, identifying the flexible parts of the complexes, and monitoring with high temporal resolution the dynamic interplay between different protein regions under physiological conditions is key to fully understanding their properties and to fostering biomedical applications. In the last decade, we have seen remarkable advances in cryo-electron microscopy (EM) techniques, which deeply transformed our vision of structural biology, especially in the field of macromolecular assemblies. With cryo-EM, detailed 3D models of large macromolecular complexes in different conformational states became readily available at atomic resolution. Concomitantly, nuclear magnetic resonance (NMR) and electron paramagnetic resonance spectroscopy (EPR) have benefited from methodological innovations which also improved the quality of the information that can be achieved. Such enhanced sensitivity widened their applicability to macromolecular complexes in environments close to physiological conditions and opened a path towards in-cell applications. In this review we will focus on the advantages and challenges of EPR techniques with an integrative approach towards a complete understanding of macromolecular structures and functions.
Collapse
Affiliation(s)
- Laura Galazzo
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Genève 4, Switzerland.
| | - Enrica Bordignon
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Genève 4, Switzerland.
| |
Collapse
|
13
|
Majeed S, Adetuyi O, Borbat PP, Majharul Islam M, Ishola O, Zhao B, Georgieva ER. Insights into the oligomeric structure of the HIV-1 Vpu protein. J Struct Biol 2023; 215:107943. [PMID: 36796461 PMCID: PMC10257199 DOI: 10.1016/j.jsb.2023.107943] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/10/2023] [Accepted: 02/11/2023] [Indexed: 02/16/2023]
Abstract
The HIV-1-encoded protein Vpu forms an oligomeric ion channel/pore in membranes and interacts with host proteins to support the virus lifecycle. However, Vpu molecular mechanisms are currently not well understood. Here, we report on the Vpu oligomeric organization under membrane and aqueous conditions and provide insights into how the Vpu environment affects the oligomer formation. For these studies, we designed a maltose-binding protein (MBP)-Vpu chimera protein and produced it in E. coli in soluble form. We analyzed this protein using analytical size-exclusion chromatography (SEC), negative staining electron microscopy (nsEM), and electron paramagnetic resonance (EPR) spectroscopy. Surprisingly, we found that MBP-Vpu formed stable oligomers in solution, seemingly driven by Vpu transmembrane domain self-association. A coarse modeling of nsEM data as well as SEC and EPR data suggests that these oligomers most likely are pentamers, similar to what was reported regarding membrane-bound Vpu. We also noticed reduced MBP-Vpu oligomer stability upon reconstitution of the protein in β-DDM detergent and mixtures of lyso-PC/PG or DHPC/DHPG. In these cases, we observed greater oligomer heterogeneity, with MBP-Vpu oligomeric order generally lower than in solution; however, larger oligomers were also present. Notably, we found that in lyso-PC/PG, above a certain protein concentration, MBP-Vpu assembles into extended structures, which had not been reported for Vpu. Therefore, we captured various Vpu oligomeric forms, which can shed light on Vpu quaternary organization. Our findings could be useful in understanding Vpu organization and function in cellular membranes and could provide information regarding the biophysical properties of single-pass transmembrane proteins.
Collapse
Affiliation(s)
- Saman Majeed
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Oluwatosin Adetuyi
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology and ACERT, Cornell University, Ithaca, NY 14853, United States
| | - Md Majharul Islam
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Olamide Ishola
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Bo Zhao
- College of Arts & Sciences Microscopy (CASM), Texas Tech University, Lubbock, TX 79409, United States
| | - Elka R Georgieva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, United States.
| |
Collapse
|
14
|
Petrich A, Dunsing V, Bobone S, Chiantia S. Influenza A M2 recruits M1 to the plasma membrane: A fluorescence fluctuation microscopy study. Biophys J 2021; 120:5478-5490. [PMID: 34808098 PMCID: PMC8715234 DOI: 10.1016/j.bpj.2021.11.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 10/16/2021] [Accepted: 11/17/2021] [Indexed: 11/17/2022] Open
Abstract
Influenza A virus (IAV) is a respiratory pathogen that causes seasonal epidemics with significant mortality. One of the most abundant proteins in IAV particles is the matrix protein 1 (M1), which is essential for the virus structural stability. M1 organizes virion assembly and budding at the plasma membrane (PM), where it interacts with other viral components. The recruitment of M1 to the PM as well as its interaction with the other viral envelope proteins (hemagglutinin [HA], neuraminidase, matrix protein 2 [M2]) is controversially discussed in previous studies. Therefore, we used fluorescence fluctuation microscopy techniques (i.e., scanning fluorescence cross-correlation spectroscopy and number and brightness) to quantify the oligomeric state of M1 and its interactions with other viral proteins in co-transfected as well as infected cells. Our results indicate that M1 is recruited to the PM by M2, as a consequence of the strong interaction between the two proteins. In contrast, only a weak interaction between M1 and HA was observed. M1-HA interaction occurred only in the event that M1 was already bound to the PM. We therefore conclude that M2 initiates the assembly of IAV by recruiting M1 to the PM, possibly allowing its further interaction with other viral proteins.
Collapse
Affiliation(s)
- Annett Petrich
- University of Potsdam, Institute of Biochemistry and Biology, Potsdam, Germany
| | - Valentin Dunsing
- University of Potsdam, Institute of Biochemistry and Biology, Potsdam, Germany
| | - Sara Bobone
- University of Rome Tor Vergata, Department of Chemical Science and Technologies, Roma, Italy
| | - Salvatore Chiantia
- University of Potsdam, Institute of Biochemistry and Biology, Potsdam, Germany.
| |
Collapse
|
15
|
Kalathingal M, Sumikama T, Oiki S, Saito S. Vectorial insertion of a β-helical peptide into membrane: a theoretical study on polytheonamide B. Biophys J 2021; 120:4786-4797. [PMID: 34555359 DOI: 10.1016/j.bpj.2021.09.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 09/07/2021] [Accepted: 09/15/2021] [Indexed: 10/20/2022] Open
Abstract
Spontaneous unidirectional, or vectorial, insertion of transmembrane peptides is a fundamental biophysical process for toxin and viral actions. Polytheonamide B (pTB) is a potent cytotoxic peptide with a β6.3-helical structure. Previous experimental studies revealed that the pTB inserts into the membrane in a vectorial fashion and forms a channel with its single molecular length long enough to span the membrane. Also, molecular dynamics simulation studies demonstrated that the pTB is prefolded in aqueous solution. These are unique features of pTB because most of the peptide toxins form channels through oligomerization of transmembrane helices. Here, we performed all-atom molecular dynamics simulations to examine the dynamic mechanism of the vectorial insertion of pTB, providing underlying elementary processes of the membrane insertion of a prefolded single transmembrane peptide. We find that the insertion of pTB proceeds with only the local lateral compression of the membrane in three successive phases: "landing," "penetration," and "equilibration" phases. The free energy calculations using the replica-exchange umbrella sampling simulations present an energy cost of 4.3 kcal/mol at the membrane surface for the membrane insertion of pTB from bulk water. The trajectories of membrane insertion revealed that the insertion process can occur in two possible pathways, namely "trapped" and "untrapped" insertions; in some cases, pTB is trapped in the upper leaflet during the penetration phase. Our simulations demonstrated the importance of membrane anchoring by the hydrophobic N-terminal blocking group in the landing phase, leading to subsequent vectorial insertion.
Collapse
Affiliation(s)
- Mahroof Kalathingal
- School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Takashi Sumikama
- PRESTO, JST, Kawaguchi, Japan; Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Shigetoshi Oiki
- Biomedical Imaging Research Center, University of Fukui, Fukui, Japan.
| | - Shinji Saito
- School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki, Japan; Institute for Molecular Science, Okazaki, Japan.
| |
Collapse
|
16
|
Majeed S, Ahmad AB, Sehar U, Georgieva ER. Lipid Membrane Mimetics in Functional and Structural Studies of Integral Membrane Proteins. MEMBRANES 2021; 11:685. [PMID: 34564502 PMCID: PMC8470526 DOI: 10.3390/membranes11090685] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 08/18/2021] [Accepted: 08/30/2021] [Indexed: 12/12/2022]
Abstract
Integral membrane proteins (IMPs) fulfill important physiological functions by providing cell-environment, cell-cell and virus-host communication; nutrients intake; export of toxic compounds out of cells; and more. However, some IMPs have obliterated functions due to polypeptide mutations, modifications in membrane properties and/or other environmental factors-resulting in damaged binding to ligands and the adoption of non-physiological conformations that prevent the protein from returning to its physiological state. Thus, elucidating IMPs' mechanisms of function and malfunction at the molecular level is important for enhancing our understanding of cell and organism physiology. This understanding also helps pharmaceutical developments for restoring or inhibiting protein activity. To this end, in vitro studies provide invaluable information about IMPs' structure and the relation between structural dynamics and function. Typically, these studies are conducted on transferred from native membranes to membrane-mimicking nano-platforms (membrane mimetics) purified IMPs. Here, we review the most widely used membrane mimetics in structural and functional studies of IMPs. These membrane mimetics are detergents, liposomes, bicelles, nanodiscs/Lipodisqs, amphipols, and lipidic cubic phases. We also discuss the protocols for IMPs reconstitution in membrane mimetics as well as the applicability of these membrane mimetic-IMP complexes in studies via a variety of biochemical, biophysical, and structural biology techniques.
Collapse
Affiliation(s)
- Saman Majeed
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Akram Bani Ahmad
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Ujala Sehar
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Elka R Georgieva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Science Center, Lubbock, TX 79409, USA
| |
Collapse
|
17
|
Thorsen MK, Lai A, Lee MW, Hoogerheide DP, Wong GCL, Freed JH, Heldwein EE. Highly Basic Clusters in the Herpes Simplex Virus 1 Nuclear Egress Complex Drive Membrane Budding by Inducing Lipid Ordering. mBio 2021; 12:e0154821. [PMID: 34425706 PMCID: PMC8406295 DOI: 10.1128/mbio.01548-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/28/2021] [Indexed: 02/01/2023] Open
Abstract
During replication of herpesviruses, capsids escape from the nucleus into the cytoplasm by budding at the inner nuclear membrane. This unusual process is mediated by the viral nuclear egress complex (NEC) that deforms the membrane around the capsid by oligomerizing into a hexagonal, membrane-bound scaffold. Here, we found that highly basic membrane-proximal regions (MPRs) of the NEC alter lipid order by inserting into the lipid headgroups and promote negative Gaussian curvature. We also find that the electrostatic interactions between the MPRs and the membranes are essential for membrane deformation. One of the MPRs is phosphorylated by a viral kinase during infection, and the corresponding phosphomimicking mutations block capsid nuclear egress. We show that the same phosphomimicking mutations disrupt the NEC-membrane interactions and inhibit NEC-mediated budding in vitro, providing a biophysical explanation for the in vivo phenomenon. Our data suggest that the NEC generates negative membrane curvature by both lipid ordering and protein scaffolding and that phosphorylation acts as an off switch that inhibits the membrane-budding activity of the NEC to prevent capsid-less budding. IMPORTANCE Herpesviruses are large viruses that infect nearly all vertebrates and some invertebrates and cause lifelong infections in most of the world's population. During replication, herpesviruses export their capsids from the nucleus into the cytoplasm by an unusual mechanism in which the viral nuclear egress complex (NEC) deforms the nuclear membrane around the capsid. However, how membrane deformation is achieved is unclear. Here, we show that the NEC from herpes simplex virus 1, a prototypical herpesvirus, uses clusters of positive charges to bind membranes and order membrane lipids. Reducing the positive charge or introducing negative charges weakens the membrane deforming ability of the NEC. We propose that the virus employs electrostatics to deform nuclear membrane around the capsid and can control this process by changing the NEC charge through phosphorylation. Blocking NEC-membrane interactions could be exploited as a therapeutic strategy.
Collapse
Affiliation(s)
- Michael K. Thorsen
- Department of Molecular Biology and Microbiology, Graduate Program in Cellular, Molecular and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Alex Lai
- Department of Chemistry and Chemical Biology and National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York, USA
| | - Michelle W. Lee
- Department of Bioengineering, Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, USA
| | - David P. Hoogerheide
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Gerard C. L. Wong
- Department of Bioengineering, Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, USA
| | - Jack H. Freed
- Department of Chemistry and Chemical Biology and National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York, USA
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Graduate Program in Cellular, Molecular and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
| |
Collapse
|
18
|
Probing Structural Dynamics of Membrane Proteins Using Electron Paramagnetic Resonance Spectroscopic Techniques. BIOPHYSICA 2021. [DOI: 10.3390/biophysica1020009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Membrane proteins are essential for the survival of living organisms. They are involved in important biological functions including transportation of ions and molecules across the cell membrane and triggering the signaling pathways. They are targets of more than half of the modern medical drugs. Despite their biological significance, information about the structural dynamics of membrane proteins is lagging when compared to that of globular proteins. The major challenges with these systems are low expression yields and lack of appropriate solubilizing medium required for biophysical techniques. Electron paramagnetic resonance (EPR) spectroscopy coupled with site directed spin labeling (SDSL) is a rapidly growing powerful biophysical technique that can be used to obtain pertinent structural and dynamic information on membrane proteins. In this brief review, we will focus on the overview of the widely used EPR approaches and their emerging applications to answer structural and conformational dynamics related questions on important membrane protein systems.
Collapse
|
19
|
Georgieva ER. Protein Conformational Dynamics upon Association with the Surfaces of Lipid Membranes and Engineered Nanoparticles: Insights from Electron Paramagnetic Resonance Spectroscopy. Molecules 2020; 25:E5393. [PMID: 33218036 PMCID: PMC7698768 DOI: 10.3390/molecules25225393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/15/2020] [Accepted: 11/16/2020] [Indexed: 11/16/2022] Open
Abstract
Detailed study of conformational rearrangements and dynamics of proteins is central to our understanding of their physiological functions and the loss of function. This review outlines the applications of the electron paramagnetic resonance (EPR) technique to study the structural aspects of proteins transitioning from a solution environment to the states in which they are associated with the surfaces of biological membranes or engineered nanoobjects. In the former case these structural transitions generally underlie functional protein states. The latter case is mostly relevant to the application of protein immobilization in biotechnological industries, developing methods for protein purification, etc. Therefore, evaluating the stability of the protein functional state is particularly important. EPR spectroscopy in the form of continuous-wave EPR or pulse EPR distance measurements in conjunction with protein spin labeling provides highly versatile and sensitive tools to characterize the changes in protein local dynamics as well as large conformational rearrangements. The technique can be widely utilized in studies of both protein-membrane and engineered nanoobject-protein complexes.
Collapse
Affiliation(s)
- Elka R Georgieva
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| |
Collapse
|
20
|
In-cell destabilization of a homodimeric protein complex detected by DEER spectroscopy. Proc Natl Acad Sci U S A 2020; 117:20566-20575. [PMID: 32788347 DOI: 10.1073/pnas.2005779117] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The complexity of the cellular medium can affect proteins' properties, and, therefore, in-cell characterization of proteins is essential. We explored the stability and conformation of the first baculoviral IAP repeat (BIR) domain of X chromosome-linked inhibitor of apoptosis (XIAP), BIR1, as a model for a homodimer protein in human HeLa cells. We employed double electron-electron resonance (DEER) spectroscopy and labeling with redox stable and rigid Gd3+ spin labels at three representative protein residues, C12 (flexible region), E22C, and N28C (part of helical residues 26 to 31) in the N-terminal region. In contrast to predictions by excluded-volume crowding theory, the dimer-monomer dissociation constant K D was markedly higher in cells than in solution and dilute cell lysate. As expected, this increase was partially recapitulated under conditions of high salt concentrations, given that conserved salt bridges at the dimer interface are critically required for association. Unexpectedly, however, also the addition of the crowding agent Ficoll destabilized the dimer while the addition of bovine serum albumin (BSA) and lysozyme, often used to represent interaction with charged macromolecules, had no effect. Our results highlight the potential of DEER for in-cell study of proteins as well as the complexities of the effects of the cellular milieu on protein structures and stability.
Collapse
|
21
|
Lindemann WR, Mijalis AJ, Alonso JL, Borbat PP, Freed JH, Arnaout MA, Pentelute BL, Ortony JH. Conformational Dynamics in Extended RGD-Containing Peptides. Biomacromolecules 2020; 21:2786-2794. [PMID: 32469507 PMCID: PMC7388056 DOI: 10.1021/acs.biomac.0c00506] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RGD is a prolific example of a tripeptide used in biomaterials for cell adhesion, but the potency of free or surface-bound RGD tripeptide is orders-of-magnitude less than the RGD domain within natural proteins. We designed a set of peptides with varying lengths, composed of fragments of fibronectin protein whose central three residues are RGD, in order to vary their conformational behavior without changing the binding site's chemical environment. With these peptides, we measure the conformational dynamics and transient structure of the active site. Our studies reveal how flanking residues affect conformational behavior and integrin binding. We find that disorder of the binding site is important to the potency of RGD peptides and that transient hydrogen bonding near the RGD site affects both the energy landscape roughness of the peptides and peptide binding. This phenomenon is independent of longer-range folding interactions and helps explain why short binding sequences, including RGD itself, do not fully replicate the integrin-targeting properties of extracellular matrix proteins. Our studies reinforce that peptide binding is a holistic event and fragments larger than those directly involved in binding should be considered in the design of peptide epitopes for functional biomaterials.
Collapse
Affiliation(s)
- William R Lindemann
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Alexander J Mijalis
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - José L Alonso
- Leukocyte Biology and Inflammation Program, Division of Nephrology and Department of Medicine, Massachusetts General Hospital, 149 13th Street, Charlestown, Massachusetts 02129, United States
- Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115, United States
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850, United States
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850, United States
| | - M Amin Arnaout
- Leukocyte Biology and Inflammation Program, Division of Nephrology and Department of Medicine, Massachusetts General Hospital, 149 13th Street, Charlestown, Massachusetts 02129, United States
- Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115, United States
| | - Bradley L Pentelute
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Julia H Ortony
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| |
Collapse
|
22
|
Sahu ID, Lorigan GA. Electron Paramagnetic Resonance as a Tool for Studying Membrane Proteins. Biomolecules 2020; 10:E763. [PMID: 32414134 PMCID: PMC7278021 DOI: 10.3390/biom10050763] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 04/24/2020] [Accepted: 04/24/2020] [Indexed: 12/13/2022] Open
Abstract
Membrane proteins possess a variety of functions essential to the survival of organisms. However, due to their inherent hydrophobic nature, it is extremely difficult to probe the structure and dynamic properties of membrane proteins using traditional biophysical techniques, particularly in their native environments. Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling (SDSL) is a very powerful and rapidly growing biophysical technique to study pertinent structural and dynamic properties of membrane proteins with no size restrictions. In this review, we will briefly discuss the most commonly used EPR techniques and their recent applications for answering structure and conformational dynamics related questions of important membrane protein systems.
Collapse
Affiliation(s)
- Indra D. Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| |
Collapse
|
23
|
Georgieva ER, Borbat PP, Fanouraki C, Freed JH. High-yield production in E. coli and characterization of full-length functional p13 II protein from human T-cell leukemia virus type 1. Protein Expr Purif 2020; 173:105659. [PMID: 32360379 DOI: 10.1016/j.pep.2020.105659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 04/20/2020] [Accepted: 04/26/2020] [Indexed: 10/24/2022]
Abstract
Human T-cell leukemia virus type 1 is an oncovirus that causes aggressive adult T-cell leukemia but is also responsible for severe neurodegenerative and endocrine disorders. Combatting HTLV-1 infections requires a detailed understanding of the viral mechanisms in the host. Therefore, in vitro studies of important virus-encoded proteins would be critical. Our focus herein is on the HTLV-1-encoded regulatory protein p13II, which interacts with the inner mitochondrial membrane, increasing its permeability to cations (predominantly potassium, K+). Thereby, this protein affects mitochondrial homeostasis. We report on our progress in developing specific protocols for heterologous expression of p13II in E. coli, and methods for its purification and characterization. We succeeded in producing large quantities of highly-pure full-length p13II, deemed to be its fully functional form. Importantly, our particular approach based on the fusion of ubiquitin to the p13II C-terminus was instrumental in increasing the persistently low expression of soluble p13II in its native form. We subsequently developed approaches for protein spin labeling and a conformation study using double electron-electron resonance (DEER) spectroscopy and a fluorescence-based cation uptake assay for p13II in liposomes. Our DEER results point to large protein conformation changes occurring upon transition from the soluble to the membrane-bound state. The functional assay on p13II-assisted transport of thallium (Tl+) through the membrane, wherein Tl+ substituted for K+, suggests transmembrane potential involvement in p13II function. Our study lays the foundation for expansion of in vitro functional and structural investigations on p13II and would aid in the development of structure-based protein inhibitors and markers.
Collapse
Affiliation(s)
- Elka R Georgieva
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY, 14853, USA.
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY, 14853, USA; ACERT Center for Advanced ESR Technology, Cornell University, Ithaca, NY, 14853, USA
| | - Christina Fanouraki
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY, 14853, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY, 14853, USA; ACERT Center for Advanced ESR Technology, Cornell University, Ithaca, NY, 14853, USA
| |
Collapse
|
24
|
Mezhenskaya D, Isakova-Sivak I, Rudenko L. M2e-based universal influenza vaccines: a historical overview and new approaches to development. J Biomed Sci 2019; 26:76. [PMID: 31629405 PMCID: PMC6800501 DOI: 10.1186/s12929-019-0572-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 10/01/2019] [Indexed: 01/04/2023] Open
Abstract
The influenza A virus was isolated for the first time in 1931, and the first attempts to develop a vaccine against the virus began soon afterwards. In addition to causing seasonal epidemics, influenza viruses can cause pandemics at random intervals, which are very hard to predict. Vaccination is the most effective way of preventing the spread of influenza infection. However, seasonal vaccination is ineffective against pandemic influenza viruses because of antigenic differences, and it takes approximately six months from isolation of a new virus to develop an effective vaccine. One of the possible ways to fight the emergence of pandemics may be by using a new type of vaccine, with a long and broad spectrum of action. The extracellular domain of the M2 protein (M2e) of influenza A virus is a conservative region, and an attractive target for a universal influenza vaccine. This review gives a historical overview of the study of M2 protein, and summarizes the latest developments in the preparation of M2e-based universal influenza vaccines.
Collapse
Affiliation(s)
- Daria Mezhenskaya
- Department of Virology, Institute of Experimental Medicine, 12 Acad. Pavlov Street, St. Petersburg, 197376, Russia
| | - Irina Isakova-Sivak
- Department of Virology, Institute of Experimental Medicine, 12 Acad. Pavlov Street, St. Petersburg, 197376, Russia.
| | - Larisa Rudenko
- Department of Virology, Institute of Experimental Medicine, 12 Acad. Pavlov Street, St. Petersburg, 197376, Russia
| |
Collapse
|
25
|
Wort JL, Ackermann K, Giannoulis A, Stewart AJ, Norman DG, Bode BE. Sub-Micromolar Pulse Dipolar EPR Spectroscopy Reveals Increasing Cu II -labelling of Double-Histidine Motifs with Lower Temperature. Angew Chem Int Ed Engl 2019; 58:11681-11685. [PMID: 31218813 PMCID: PMC6771633 DOI: 10.1002/anie.201904848] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 06/03/2019] [Indexed: 12/20/2022]
Abstract
Electron paramagnetic resonance (EPR) distance measurements are making increasingly important contributions to the studies of biomolecules by providing highly accurate geometric constraints. Combining double-histidine motifs with CuII spin labels can further increase the precision of distance measurements. It is also useful for proteins containing essential cysteines that can interfere with thiol-specific labelling. However, the non-covalent CuII coordination approach is vulnerable to low binding-affinity. Herein, dissociation constants (KD ) are investigated directly from the modulation depths of relaxation-induced dipolar modulation enhancement (RIDME) EPR experiments. This reveals low- to sub-μm CuII KD s under EPR distance measurement conditions at cryogenic temperatures. We show the feasibility of exploiting the double-histidine motif for EPR applications even at sub-μm protein concentrations in orthogonally labelled CuII -nitroxide systems using a commercial Q-band EPR instrument.
Collapse
Affiliation(s)
- Joshua L. Wort
- EaStCHEM School of ChemistryBiomedical Sciences Research Complex, and Centre of Magnetic ResonanceUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | - Katrin Ackermann
- EaStCHEM School of ChemistryBiomedical Sciences Research Complex, and Centre of Magnetic ResonanceUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | - Angeliki Giannoulis
- EaStCHEM School of ChemistryBiomedical Sciences Research Complex, and Centre of Magnetic ResonanceUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | - Alan J. Stewart
- School of MedicineBiomedical Sciences Research Complex, and Centre of Magnetic ResonanceUniversity of St AndrewsNorth HaughSt AndrewsKY16 9TFUK
| | - David G. Norman
- School of Life SciencesUniversity of Dundee, Medical Sciences InstituteDundeeDD1 5EHUK
| | - Bela E. Bode
- EaStCHEM School of ChemistryBiomedical Sciences Research Complex, and Centre of Magnetic ResonanceUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| |
Collapse
|
26
|
Wort JL, Ackermann K, Giannoulis A, Stewart AJ, Norman DG, Bode BE. Sub‐Micromolar Pulse Dipolar EPR Spectroscopy Reveals Increasing Cu
II
‐labelling of Double‐Histidine Motifs with Lower Temperature. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201904848] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Joshua L. Wort
- EaStCHEM School of Chemistry Biomedical Sciences Research Complex, and Centre of Magnetic Resonance University of St Andrews North Haugh St Andrews KY16 9ST UK
| | - Katrin Ackermann
- EaStCHEM School of Chemistry Biomedical Sciences Research Complex, and Centre of Magnetic Resonance University of St Andrews North Haugh St Andrews KY16 9ST UK
| | - Angeliki Giannoulis
- EaStCHEM School of Chemistry Biomedical Sciences Research Complex, and Centre of Magnetic Resonance University of St Andrews North Haugh St Andrews KY16 9ST UK
| | - Alan J. Stewart
- School of Medicine Biomedical Sciences Research Complex, and Centre of Magnetic Resonance University of St Andrews North Haugh St Andrews KY16 9TF UK
| | - David G. Norman
- School of Life Sciences University of Dundee, Medical Sciences Institute Dundee DD1 5EH UK
| | - Bela E. Bode
- EaStCHEM School of Chemistry Biomedical Sciences Research Complex, and Centre of Magnetic Resonance University of St Andrews North Haugh St Andrews KY16 9ST UK
| |
Collapse
|
27
|
Insights into histidine kinase activation mechanisms from the monomeric blue light sensor EL346. Proc Natl Acad Sci U S A 2019; 116:4963-4972. [PMID: 30808807 DOI: 10.1073/pnas.1813586116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Translation of environmental cues into cellular behavior is a necessary process in all forms of life. In bacteria, this process frequently involves two-component systems in which a sensor histidine kinase (HK) autophosphorylates in response to a stimulus before subsequently transferring the phosphoryl group to a response regulator that controls downstream effectors. Many details of the molecular mechanisms of HK activation are still unclear due to complications associated with the multiple signaling states of these large, multidomain proteins. To address these challenges, we combined complementary solution biophysical approaches to examine the conformational changes upon activation of a minimal, blue-light-sensing histidine kinase from Erythrobacter litoralis HTCC2594, EL346. Our data show that multiple conformations coexist in the dark state of EL346 in solution, which may explain the enzyme's residual dark-state activity. We also observe that activation involves destabilization of the helices in the dimerization and histidine phosphotransfer-like domain, where the phosphoacceptor histidine resides, and their interactions with the catalytic domain. Similar light-induced changes occur to some extent even in constitutively active or inactive mutants, showing that light sensing can be decoupled from activation of kinase activity. These structural changes mirror those inferred by comparing X-ray crystal structures of inactive and active HK fragments, suggesting that they are at the core of conformational changes leading to HK activation. More broadly, our findings uncover surprising complexity in this simple system and allow us to outline a mechanism of the multiple steps of HK activation.
Collapse
|
28
|
Tauroursodeoxycholic acid (TUDCA) inhibits influenza A viral infection by disrupting viral proton channel M2. Sci Bull (Beijing) 2019; 64:180-188. [PMID: 32288967 PMCID: PMC7104969 DOI: 10.1016/j.scib.2018.08.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 06/22/2018] [Accepted: 07/22/2018] [Indexed: 01/20/2023]
Abstract
Influenza is a persistent threat to human health and there is a continuing requirement for updating anti-influenza strategies. Initiated by observations of different endoplasmic reticulum (ER) responses of host to seasonal H1N1 and highly pathogenic avian influenza (HPAI) A H5N1 infections, we identified an alternative antiviral role of tauroursodeoxycholic acid (TUDCA), a clinically available ER stress inhibitor, both in vitro and in vivo. Rather than modulating ER stress in host cells, TUDCA abolished the proton conductivity of viral M2 by disrupting its oligomeric states, which induces inefficient viral infection. We also showed that M2 penetrated cells, whose intracellular uptake depended on its proton channel activity, an effect observed in both TUDCA and M2 inhibitor amantadine. The identification and application of TUDCA as an inhibitor of M2 proton channel will expand our understanding of IAV biology and complement current anti-IAV arsenals.
Collapse
|
29
|
Baliga C, Selmke B, Worobiew I, Borbat P, Sarma SP, Trommer WE, Varadarajan R, Aghera N. CcdB at pH 4 Forms a Partially Unfolded State with a Dry Core. Biophys J 2019; 116:807-817. [PMID: 30777307 DOI: 10.1016/j.bpj.2019.01.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 01/18/2019] [Accepted: 01/23/2019] [Indexed: 12/14/2022] Open
Abstract
pH is an important factor that affects the protein structure, stability, and activity. Here, we probe the nature of the low-pH structural form of the homodimeric CcdB (controller of cell death B) protein. Characterization of CcdB protein at pH 4 and 300 K using circular dichroism spectroscopy, 8-anilino-1-naphthalene-sulphonate binding, and Trp solvation studies suggests that it forms a partially unfolded state with a dry core at equilibrium under these conditions. CcdB remains dimeric at pH 4 as shown by multiple techniques, such as size-exclusion chromatography coupled to multiangle light scattering, analytical ultracentrifugation, and electron paramagnetic resonance. Comparative analysis using two-dimensional 15N-1H heteronuclear single-quantum coherence NMR spectra of CcdB at pH 4 and 7 suggests that the pH 4 and native state have similar but nonidentical structures. Hydrogen-exchange-mass-spectrometry studies demonstrate that the pH 4 state has substantial but anisotropic changes in local stability with core regions close to the dimer interface showing lower protection but some other regions showing higher protection relative to pH 7.
Collapse
Affiliation(s)
- Chetana Baliga
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Benjamin Selmke
- Department of Chemistry, TU Kaiserslautern, Kaiserslautern, Germany
| | - Irina Worobiew
- Department of Chemistry, TU Kaiserslautern, Kaiserslautern, Germany
| | - Peter Borbat
- Department of Chemistry and Chemical Biology, ACERT National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, New York
| | - Siddhartha P Sarma
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | | | - Raghavan Varadarajan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India; Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India
| | - Nilesh Aghera
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
| |
Collapse
|
30
|
Merz GE, Borbat PP, Muok AR, Srivastava M, Bunck DN, Freed JH, Crane BR. Site-Specific Incorporation of a Cu 2+ Spin Label into Proteins for Measuring Distances by Pulsed Dipolar Electron Spin Resonance Spectroscopy. J Phys Chem B 2018; 122:9443-9451. [PMID: 30222354 DOI: 10.1021/acs.jpcb.8b05619] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Pulsed dipolar electron spin resonance spectroscopy (PDS) is a powerful tool for measuring distances in solution-state macromolecules. Paramagnetic metal ions, such as Cu2+, are used as spin probes because they can report on metalloprotein features and can be spectroscopically distinguished from traditional nitroxide (NO)-based labels. Here, we demonstrate site-specific incorporation of Cu2+ into non-metalloproteins through the use of a genetically encodable non-natural amino acid, 3-pyrazolyltyrosine (PyTyr). We first incorporate PyTyr in cyan fluorescent protein to measure Cu2+-to-NO distances and examine the effects of solvent conditions on Cu2+ binding and protein aggregation. We then apply the method to characterize the complex formed by the histidine kinase CheA and its target response regulator CheY. The X-ray structure of CheY-PyTyr confirms Cu labeling at PyTyr but also reveals a secondary Cu site. Cu2+-to-NO and Cu2+-to-Cu2+ PDS measurements of CheY-PyTyr with nitroxide-labeled CheA provide new insights into the conformational landscape of the phosphotransfer complex and have implications for kinase regulation.
Collapse
Affiliation(s)
- Gregory E Merz
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Alise R Muok
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Madhur Srivastava
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - David N Bunck
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Jack H Freed
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Brian R Crane
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| |
Collapse
|
31
|
Selmke B, Borbat PP, Nickolaus C, Varadarajan R, Freed JH, Trommer WE. Open and Closed Form of Maltose Binding Protein in Its Native and Molten Globule State As Studied by Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2018; 57:5507-5512. [PMID: 30004675 PMCID: PMC6211580 DOI: 10.1021/acs.biochem.8b00322] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An intensively investigated intermediate state of protein folding is the molten globule (MG) state, which contains secondary but hardly any tertiary structure. In previous work, we have determined the distances between interacting spins within maltose binding protein (MBP) in its native state using continuous wave and double electron-electron resonance (DEER) electron paramagnetic resonance (EPR) spectroscopy. Seven double mutants had been employed to investigate the structure within the two domains of MBP. DEER data nicely corroborated the previously available X-ray data. Even in its MG state, MBP is known to still bind its ligand maltose. We therefore hypothesized that there must be a defined structure around the binding pocket of MBP already in the absence of tertiary structure. Here we have investigated the functional and structural difference between native and MG state in the open and closed form with a new set of MBP mutants. In these, the spin-label positions were placed near the active site. Binding of its ligands leads to a conformational change from open to closed state, where the two domains are more closely together. The complete set of MBP mutants was analyzed at pH 3.2 (MG) and pH 7.4 (native state) using double-quantum coherence EPR. The values were compared with theoretical predictions of distances between the labels in biradicals constructed by molecular modeling from the crystal structures of MBP in open and closed form and were found to be in excellent agreement. Measurements show a defined structure around the binding pocket of MBP in MG, which explains maltose binding. A new and important finding is that in both states ligand-free MBP can be found in open and closed form, while ligand-bound MBP appears only in closed form because of maltose binding.
Collapse
Affiliation(s)
- Benjamin Selmke
- Department of Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern, Germany
| | - Peter P. Borbat
- Department of Chemistry and Chemical Biology, ACERT National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, NY 14853-1301, USA
| | - Chen Nickolaus
- Department of Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern, Germany
| | | | - Jack H. Freed
- Department of Chemistry and Chemical Biology, ACERT National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, NY 14853-1301, USA
| | - Wolfgang E. Trommer
- Department of Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 54, 67663 Kaiserslautern, Germany
| |
Collapse
|
32
|
Riederer EA, Focke PJ, Georgieva ER, Akyuz N, Matulef K, Borbat PP, Freed JH, Blanchard SC, Boudker O, Valiyaveetil FI. A facile approach for the in vitro assembly of multimeric membrane transport proteins. eLife 2018; 7:36478. [PMID: 29889023 PMCID: PMC6025958 DOI: 10.7554/elife.36478] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 06/08/2018] [Indexed: 11/13/2022] Open
Abstract
Membrane proteins such as ion channels and transporters are frequently homomeric. The homomeric nature raises important questions regarding coupling between subunits and complicates the application of techniques such as FRET or DEER spectroscopy. These challenges can be overcome if the subunits of a homomeric protein can be independently modified for functional or spectroscopic studies. Here, we describe a general approach for in vitro assembly that can be used for the generation of heteromeric variants of homomeric membrane proteins. We establish the approach using GltPh, a glutamate transporter homolog that is trimeric in the native state. We use heteromeric GltPh transporters to directly demonstrate the lack of coupling in substrate binding and demonstrate how heteromeric transporters considerably simplify the application of DEER spectroscopy. Further, we demonstrate the general applicability of this approach by carrying out the in vitro assembly of VcINDY, a Na+-coupled succinate transporter and CLC-ec1, a Cl-/H+ antiporter.
Collapse
Affiliation(s)
- Erika A Riederer
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, United States
| | - Paul J Focke
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, United States
| | - Elka R Georgieva
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, Unites States.,National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States
| | | | - Kimberly Matulef
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, United States
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, Unites States.,National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, Unites States.,National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, United States
| | | | - Olga Boudker
- Weill Cornell Medicine, New York, United States.,Howard Hughes Medical Institute, Maryland, United States
| | - Francis I Valiyaveetil
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, United States
| |
Collapse
|
33
|
Sahu ID, Lorigan GA. Site-Directed Spin Labeling EPR for Studying Membrane Proteins. BIOMED RESEARCH INTERNATIONAL 2018; 2018:3248289. [PMID: 29607317 PMCID: PMC5828257 DOI: 10.1155/2018/3248289] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 12/21/2017] [Indexed: 01/13/2023]
Abstract
Site-directed spin labeling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy is a rapidly expanding powerful biophysical technique to study the structural and dynamic properties of membrane proteins in a native environment. Membrane proteins are responsible for performing important functions in a wide variety of complicated biological systems that are responsible for the survival of living organisms. In this review, a brief introduction of the most popular SDSL EPR techniques and illustrations of recent applications for studying pertinent structural and dynamic properties on membrane proteins will be discussed.
Collapse
Affiliation(s)
- Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| |
Collapse
|
34
|
Affiliation(s)
- Katrin Ackermann
- Biomedical Sciences Research Complex, Centre of Magnetic Resonance and EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, Scotland
| | - Bela E. Bode
- Biomedical Sciences Research Complex, Centre of Magnetic Resonance and EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, Scotland
| |
Collapse
|
35
|
Influenza A Virus M2 Protein: Roles from Ingress to Egress. Int J Mol Sci 2017; 18:ijms18122649. [PMID: 29215568 PMCID: PMC5751251 DOI: 10.3390/ijms18122649] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 12/04/2017] [Accepted: 12/05/2017] [Indexed: 11/17/2022] Open
Abstract
Influenza A virus (IAV) matrix protein 2 (M2) is among the smallest bona fide, hence extensively studied, ion channel proteins. The M2 ion channel activity is not only essential for virus replication, but also involved in modulation of cellular homeostasis in a variety of ways. It is also the target for ion channel inhibitors, i.e., anti-influenza drugs. Thus far, several studies have been conducted to elucidate its biophysical characteristics, structure-function relationships of the ion channel, and the M2-host interactome. In this review, we discuss M2 protein synthesis and assembly into an ion channel, its roles in IAV replication, and the pathophysiological impact on the host cell.
Collapse
|
36
|
Oligomeric Structure of Anabaena Sensory Rhodopsin in a Lipid Bilayer Environment by Combining Solid-State NMR and Long-range DEER Constraints. J Mol Biol 2017; 429:1903-1920. [DOI: 10.1016/j.jmb.2017.05.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 04/27/2017] [Accepted: 05/06/2017] [Indexed: 11/22/2022]
|
37
|
Jeong BS, Dyer RB. Proton Transport Mechanism of M2 Proton Channel Studied by Laser-Induced pH Jump. J Am Chem Soc 2017; 139:6621-6628. [PMID: 28467842 DOI: 10.1021/jacs.7b00617] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The M2 proton transport channel of the influenza virus A is an important model system because it conducts protons with high selectivity and unidirectionally when activated at low pH, despite the relative simplicity of its structure. Although it has been studied extensively, the molecular details of the pH-dependent gating and proton conductance mechanisms are incompletely understood. We report direct observation of the M2 proton channel activation process using a laser-induced pH jump coupled with tryptophan fluorescence as a probe. Biphasic kinetics is observed, with the fast phase corresponding to the His37 protonation, and the slow phase associated with the subsequent conformation change. Unusually fast His37 protonation was observed (2.0 × 1010 M-1 s-1), implying the existence of proton collecting antennae for expedited proton transport. The conformation change (4 × 103 s-1) was about 2 orders of magnitude slower than protonation at endosomal pH, suggesting that a transporter model is likely not feasible.
Collapse
Affiliation(s)
- Ban-Seok Jeong
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
| | - R Brian Dyer
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
| |
Collapse
|
38
|
Barniol-Xicota M, Gazzarrini S, Torres E, Hu Y, Wang J, Naesens L, Moroni A, Vázquez S. Slow but Steady Wins the Race: Dissimilarities among New Dual Inhibitors of the Wild-Type and the V27A Mutant M2 Channels of Influenza A Virus. J Med Chem 2017; 60:3727-3738. [PMID: 28418242 DOI: 10.1021/acs.jmedchem.6b01758] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
New insights on the amantadine resistance mechanism of the V27A mutant were obtained through the study of novel, easily accessible 4-(1- and 2-adamantyl)piperidines, identified as dual binders of the wild-type and V27A mutant M2 channels of influenza A virus. Their antiviral activity and channel blocking ability were determined using cell-based assays and two-electrode voltage clamp (TEVC) technique on M2 channels, respectively. In addition, electrophysiology experiments revealed two interesting findings: (i) these inhibitors display a different behavior against the wild-type versus V27A mutant A/M2 channels, and (ii) the compounds display antiviral activity when they have kd equal or smaller than 10-6 while they do not exhibit antiviral activity when kd is 10-5 or higher although they may show blocking activity in the TEV assay. Thus, caution must be taken when predicting antiviral activity based on percent channel blockage in electrophysiological assays. These findings provide experimental evidence of the resistance mechanism of the V27A mutation to wild-type inhibitors, previously predicted in silico, offer an explanation for the lack of antiviral activity of compounds active in the TEV assay, and may help design new and more effective drugs.
Collapse
Affiliation(s)
- Marta Barniol-Xicota
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| | - Sabrina Gazzarrini
- Department of Biosciences and National Research Council (CNR) Biophysics Institute (IBF), University of Milan , Via Celoria 26, 20133 Milan, Italy
| | - Eva Torres
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| | - Yanmei Hu
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona , Tucson, Arizona 85721, United States.,BI05 Institute, The University of Arizona , Tucson, Arizona 85721, United States
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona , Tucson, Arizona 85721, United States.,BI05 Institute, The University of Arizona , Tucson, Arizona 85721, United States
| | - Lieve Naesens
- Rega Institute for Medical Research, KU Leuven , B-3000 Leuven, Belgium
| | - Anna Moroni
- Department of Biosciences and National Research Council (CNR) Biophysics Institute (IBF), University of Milan , Via Celoria 26, 20133 Milan, Italy
| | - Santiago Vázquez
- Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona , Av. Joan XXIII, 27-31, Barcelona E-08028, Spain
| |
Collapse
|
39
|
Sukomon N, Widom J, Borbat PP, Freed JH, Crane BR. Stability and Conformation of a Chemoreceptor HAMP Domain Chimera Correlates with Signaling Properties. Biophys J 2017; 112:1383-1395. [PMID: 28402881 PMCID: PMC5390053 DOI: 10.1016/j.bpj.2017.02.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 02/15/2017] [Accepted: 02/21/2017] [Indexed: 12/15/2022] Open
Abstract
HAMP domains are dimeric, four-helix bundles that transduce conformational signals in bacterial receptors. Genetic studies of the Escherichia coli serine receptor (Tsr) provide an opportunity to understand HAMP conformational behavior in terms of functional output. To increase its stability, the Tsr HAMP domain was spliced into a poly-HAMP unit from the Pseudomonas aeruginosa Aer2 receptor. Within the chimera, the Tsr HAMP undergoes a thermal melting transition at a temperature much lower than that of the Aer2 HAMP domains. Pulse-dipolar electron spin resonance spectroscopy and site-specific spin-labeling confirm that the Tsr HAMP maintains a four-helix bundle. Pulse-dipolar electron spin resonance spectroscopy was also used to study three well-characterized HAMP mutational phenotypes: those that cause flagella rotation that is counterclockwise (CCW) A and kinase-off; CCW B and also kinase-off; and, clockwise (CW) and kinase-on. Conformational properties of the three HAMP variants support a biphasic model of dynamic bundle stability, but also indicate distinct conformational changes within the helix bundle. Functional kinase-on (CW) and kinase-off (CCW A) states differ by concerted changes in the positions of spin-label sites at the base of the bundle. Opposite shifts in the subunit separation distances of neighboring residues at the C-termini of the α1 and α2 helices are consistent with a helix scissors motion or a gearbox rotational model of HAMP activation. In the drastic kinase-off lesion of CCW B, the α1 helices unfold and the α2 helices form a tight two-helix coiled-coil. The substitution of a critical residue in the Tsr N-terminal linker or control cable reduces conformational heterogeneity at the N-terminus of α1 but does not affect structure at the C-terminus of α2. Overall, the data suggest that transitions from on- to off-states involve decreased motional amplitudes of the Tsr HAMP coupled with helix rotations and movements toward a two-helix packing mode.
Collapse
Affiliation(s)
- Nattakan Sukomon
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York
| | - Joanne Widom
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York; National Biomedical Center for Advanced ESR Technologies, Cornell University, Ithaca, New York
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York; National Biomedical Center for Advanced ESR Technologies, Cornell University, Ithaca, New York
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York.
| |
Collapse
|
40
|
Li J, Qiu XJ. Quantification of Membrane Protein Self-Association with a High-Throughput Compatible Fluorescence Assay. Biochemistry 2017; 56:1951-1954. [PMID: 28333446 DOI: 10.1021/acs.biochem.7b00009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
For many membrane proteins, self-association serves both structural and functional roles. Studies of such association can be simplified by switching to micelles as the membrane-mimicking environment, but native interaction is not preserved in all detergents. The selection of suitable conditions for biochemical experiments would be greatly facilitated by a quantitative high-throughput assay. Here we showed that the fluorescence polarization reduction, which resulted from homo-Förster resonance energy transfer and was measured in a high-throughput compatible format, can be used to determine both association states and constants for membrane proteins in micelles.
Collapse
Affiliation(s)
- Junbei Li
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University , Suzhou, Jiangsu 215123, China
| | - Xiaoyan J Qiu
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University , Suzhou, Jiangsu 215123, China
| |
Collapse
|
41
|
Srivastava M, Georgieva ER, Freed JH. A New Wavelet Denoising Method for Experimental Time-Domain Signals: Pulsed Dipolar Electron Spin Resonance. J Phys Chem A 2017; 121:2452-2465. [PMID: 28257206 DOI: 10.1021/acs.jpca.7b00183] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We adapt a new wavelet-transform-based method of denoising experimental signals to pulse-dipolar electron-spin resonance spectroscopy (PDS). We show that signal averaging times of the time-domain signals can be reduced by as much as 2 orders of magnitude, while retaining the fidelity of the underlying signals, in comparison with noiseless reference signals. We have achieved excellent signal recovery when the initial noisy signal has an SNR ≳ 3. This approach is robust and is expected to be applicable to other time-domain spectroscopies. In PDS, these time-domain signals representing the dipolar interaction between two electron spin labels are converted into their distance distribution functions P(r), usually by regularization methods such as Tikhonov regularization. The significant improvements achieved by using denoised signals for this regularization are described. We show that they yield P(r)'s with more accurate detail and yield clearer separations of respective distances, which is especially important when the P(r)'s are complex. Also, longer distance P(r)'s, requiring longer dipolar evolution times, become accessible after denoising. In comparison to standard wavelet denoising approaches, it is clearly shown that the new method (WavPDS) is superior.
Collapse
Affiliation(s)
- Madhur Srivastava
- National Biomedical Center for Advanced ESR Technology, ‡Meinig School of Biomedical Engineering, and §Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
| | - Elka R Georgieva
- National Biomedical Center for Advanced ESR Technology, ‡Meinig School of Biomedical Engineering, and §Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
| | - Jack H Freed
- National Biomedical Center for Advanced ESR Technology, ‡Meinig School of Biomedical Engineering, and §Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States
| |
Collapse
|
42
|
Eschmann NA, Georgieva ER, Ganguly P, Borbat PP, Rappaport MD, Akdogan Y, Freed JH, Shea JE, Han S. Signature of an aggregation-prone conformation of tau. Sci Rep 2017; 7:44739. [PMID: 28303942 PMCID: PMC5356194 DOI: 10.1038/srep44739] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 02/13/2017] [Indexed: 11/09/2022] Open
Abstract
The self-assembly of the microtubule associated tau protein into fibrillar cell inclusions is linked to a number of devastating neurodegenerative disorders collectively known as tauopathies. The mechanism by which tau self-assembles into pathological entities is a matter of much debate, largely due to the lack of direct experimental insights into the earliest stages of aggregation. We present pulsed double electron-electron resonance measurements of two key fibril-forming regions of tau, PHF6 and PHF6*, in transient as aggregation happens. By monitoring the end-to-end distance distribution of these segments as a function of aggregation time, we show that the PHF6(*) regions dramatically extend to distances commensurate with extended β-strand structures within the earliest stages of aggregation, well before fibril formation. Combined with simulations, our experiments show that the extended β-strand conformational state of PHF6(*) is readily populated under aggregating conditions, constituting a defining signature of aggregation-prone tau, and as such, a possible target for therapeutic interventions.
Collapse
Affiliation(s)
- Neil A Eschmann
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, 93106, USA
| | - Elka R Georgieva
- National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, New York, 14853, USA.,Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, 14853, USA
| | - Pritam Ganguly
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, 93106, USA
| | - Peter P Borbat
- National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, New York, 14853, USA.,Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, 14853, USA
| | - Maxime D Rappaport
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, 93106, USA
| | - Yasar Akdogan
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, 93106, USA
| | - Jack H Freed
- National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, New York, 14853, USA.,Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, 14853, USA
| | - Joan-Emma Shea
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, 93106, USA
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, 93106, USA
| |
Collapse
|
43
|
Kao TY, Tsai CJ, Lan YJ, Chiang YW. The role of conformational heterogeneity in regulating the apoptotic activity of BAX protein. Phys Chem Chem Phys 2017; 19:9584-9591. [DOI: 10.1039/c7cp00401j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Inactive BAX exists in two states. A shift in the equilibrium would initiate apoptosis.
Collapse
Affiliation(s)
- Te-Yu Kao
- Department of Chemistry
- National Tsing Hua University
- Hsinchu 30013
- Taiwan
| | - Chia-Jung Tsai
- Department of Chemistry
- National Tsing Hua University
- Hsinchu 30013
- Taiwan
| | - Yu-Jing Lan
- Department of Chemistry
- National Tsing Hua University
- Hsinchu 30013
- Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry
- National Tsing Hua University
- Hsinchu 30013
- Taiwan
| |
Collapse
|
44
|
Georgieva ER, Borbat PP, Grushin K, Stoilova-McPhie S, Kulkarni NJ, Liang Z, Freed JH. Conformational Response of Influenza A M2 Transmembrane Domain to Amantadine Drug Binding at Low pH (pH 5.5). Front Physiol 2016; 7:317. [PMID: 27524969 PMCID: PMC4965473 DOI: 10.3389/fphys.2016.00317] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/13/2016] [Indexed: 12/27/2022] Open
Abstract
The M2 protein from influenza A plays important roles in its viral cycle. It contains a single transmembrane helix, which oligomerizes into a homotetrameric proton channel that conducts in the low-pH environment of the host-cell endosome and Golgi apparatus, leading to virion uncoating at an early stage of infection. We studied conformational rearrangements that occur in the M2 core transmembrane domain residing on the lipid bilayer, flanked by juxtamembrane residues (M2TMD21-49 fragment), upon its interaction with amantadine drug at pH 5.5 when M2 is conductive. We also tested the role of specific mutation and lipid chain length. Electron spin resonance (ESR) spectroscopy and electron microscopy were applied to M2TMD21-49, labeled at the residue L46C with either nitroxide spin-label or Nanogold® reagent, respectively. Electron microscopy confirmed that M2TMD21-49 reconstituted into DOPC/POPS at 1:10,000 peptide-to-lipid molar ratio (P/L) either with or without amantadine, is an admixture of monomers, dimers, and tetramers, confirming our model based on a dimer intermediate in the assembly of M2TMD21-49. As reported by double electron-electron resonance (DEER), in DOPC/POPS membranes amantadine shifts oligomer equilibrium to favor tetramers, as evidenced by an increase in DEER modulation depth for P/L's ranging from 1:18,000 to 1:160. Furthermore, amantadine binding shortens the inter-spin distances (for nitroxide labels) by 5-8 Å, indicating drug induced channel closure on the C-terminal side. No such effect was observed for the thinner membrane of DLPC/DLPS, emphasizing the role of bilayer thickness. The analysis of continuous wave (cw) ESR spectra of spin-labeled L46C residue provides additional support to a more compact helix bundle in amantadine-bound M2TMD 21-49 through increased motional ordering. In contrast to wild-type M2TMD21-49, the amantadine-bound form does not exhibit noticeable conformational changes in the case of G34A mutation found in certain drug-resistant influenza strains. Thus, the inhibited M2TMD21-49 channel is a stable tetramer with a closed C-terminal exit pore. This work is aimed at contributing to the development of structure-based anti-influenza pharmaceuticals.
Collapse
Affiliation(s)
- Elka R Georgieva
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| | - Kirill Grushin
- Department of Neuroscience and Cell Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston Galveston, TX, USA
| | - Svetla Stoilova-McPhie
- Department of Neuroscience and Cell Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston Galveston, TX, USA
| | | | - Zhichun Liang
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| |
Collapse
|
45
|
Ho CS, Khadka NK, She F, Cai J, Pan J. Influenza M2 Transmembrane Domain Senses Membrane Heterogeneity and Enhances Membrane Curvature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6730-6738. [PMID: 27285399 PMCID: PMC5131574 DOI: 10.1021/acs.langmuir.6b00150] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Targeting host cell membranes by M2 of influenza A virus is important for virus invasion and replication. We study the transmembrane domain of M2 (M2TM) interacting with mica-supported planar bilayers and free-standing giant unilamellar vesicles (GUVs). Using solution atomic force microscopy (AFM), we show that the size of M2TM oligomers is dependent on lipid composition. The addition of M2TM to lipid bilayers containing liquid-ordered (Lo) and liquid-disordered (Ld) phases reveals that M2TM preferentially partitions into the Ld phase; phase-dependent partitioning results in a larger rigidity of the Ld phase. We next use fluorescence microscopy to study the effects of M2TM on phase-coexisting GUVs. In particular, M2TM is found to increase GUVs' miscibility transition temperature Tmix. The augmented thermodynamic stability can be accounted for by considering an enhanced energy barrier of lipid mixing between coexisting phases. Our GUV study also shows that M2TM can elicit an array of vesicle shapes mimicking virus budding. M2TM enhanced membrane curvature is consistent with our AFM data, which show altered membrane rigidity and consequently line tension at domain edges. Together, our results highlight that in addition to conducting protons, M2TM can actively regulate membrane heterogeneity and augment membrane curvature.
Collapse
Affiliation(s)
- Chian Sing Ho
- Department of Physics, University of South Florida, Tampa, FL 33620, United States
| | - Nawal K. Khadka
- Department of Physics, University of South Florida, Tampa, FL 33620, United States
| | - Fengyu She
- Department of Chemistry, University of South Florida, Tampa, FL 33620, United States
| | - Jianfeng Cai
- Department of Chemistry, University of South Florida, Tampa, FL 33620, United States
| | - Jianjun Pan
- Department of Physics, University of South Florida, Tampa, FL 33620, United States
| |
Collapse
|
46
|
Jhong SR, Li CY, Sung TC, Lan YJ, Chang KJ, Chiang YW. Evidence for an Induced-Fit Process Underlying the Activation of Apoptotic BAX by an Intrinsically Disordered BimBH3 Peptide. J Phys Chem B 2016; 120:2751-60. [PMID: 26913490 DOI: 10.1021/acs.jpcb.6b00909] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Apoptotic BAX protein functions as a critical gateway to mitochondria-mediated apoptosis. A diversity of stimuli has been implicated in initiating BAX activation, but the triggering mechanism remains elusive. Here we study the interaction of BAX with an intrinsically disordered BH3 motif of Bim protein (BimBH3) using ESR techniques. Upon incubation with BAX, BimBH3 binds to BAX at helices 1/6 trigger site to initiate conformational changes of BAX, which in turn promotes the formation of BAX oligomers. The study strategy is twofold: while BAX oligomerization was monitored through spectral changes of spin-labeled BAX, the binding kinetics was studied by observing time-dependent changes of spin-labeled BimBH3. Meanwhile, conformational transition between the unstructured and structured BimBH3 was measured. We show that helical propensity of the BimBH3 is increased upon binding to BAX but is then reduced after being released from the activated BAX; the release is due to the BimBH3-induced conformational change of BAX that is a prerequisite for the oligomer assembling. Intermediate states are identified, offering a key snapshot of the coupled folding and binding process. Our results provide a quantitative mechanistic description of the BAX activation and reveal new insights into the mechanism underlying the interactions between BAX and BH3-mimetic peptide.
Collapse
Affiliation(s)
- Siao-Ru Jhong
- Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Ching-Yu Li
- Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Tai-Ching Sung
- Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Yu-Jing Lan
- Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Kuo-Jung Chang
- Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan
| |
Collapse
|
47
|
Abstract
Membrane proteins are very important in controlling bioenergetics, functional activity, and initializing signal pathways in a wide variety of complicated biological systems. They also represent approximately 50% of the potential drug targets. EPR spectroscopy is a very popular and powerful biophysical tool that is used to study the structural and dynamic properties of membrane proteins. In this article, a basic overview of the most commonly used EPR techniques and examples of recent applications to answer pertinent structural and dynamic related questions on membrane protein systems will be presented.
Collapse
Affiliation(s)
- Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, United States of America
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, United States of America
| |
Collapse
|