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Sun X, Eastman G, Shi Y, Saibaba S, Oliveira AK, Lukens JR, Norambuena A, Thompson JA, Purdy MD, Dryden K, Pardo E, Mandell JW, Bloom GS. Structural and functional damage to neuronal nuclei caused by extracellular tau oligomers. Alzheimers Dement 2024; 20:1656-1670. [PMID: 38069673 PMCID: PMC10947977 DOI: 10.1002/alz.13535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 09/06/2023] [Accepted: 10/11/2023] [Indexed: 12/19/2023]
Abstract
INTRODUCTION Neuronal nuclei are normally smoothly surfaced. In Alzheimer's disease (AD) and other tauopathies, though, they often develop invaginations. We investigated mechanisms and functional consequences of neuronal nuclear invagination in tauopathies. METHODS Nuclear invagination was assayed by immunofluorescence in the brain, and in cultured neurons before and after extracellular tau oligomer (xcTauO) exposure. Nucleocytoplasmic transport was assayed in cultured neurons. Gene expression was investigated using nanoString nCounter technology and quantitative reverse transcription polymerase chain reaction. RESULTS Invaginated nuclei were twice as abundant in human AD as in cognitively normal adults, and were increased in mouse neurodegeneration models. In cultured neurons, nuclear invagination was induced by xcTauOs by an intracellular tau-dependent mechanism. xcTauOs impaired nucleocytoplasmic transport, increased histone H3 trimethylation at lysine 9, and altered gene expression, especially by increasing tau mRNA. DISCUSSION xcTauOs may be a primary cause of nuclear invagination in vivo, and by extension, impair nucleocytoplasmic transport and induce pathogenic gene expression changes. HIGHLIGHTS Extracellular tau oligomers (xcTauOs) cause neuronal nuclei to invaginate. xcTauOs alter nucleocytoplasmic transport, chromatin structure, and gene expression. The most upregulated gene is MAPT, which encodes tau. xcTauOs may thus drive a positive feedback loop for production of toxic tau.
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Affiliation(s)
- Xuehan Sun
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Guillermo Eastman
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
- Departamento de GenómicaInstituto de Investigaciones Biológicas Clemente EstableMinisterio de Educación y CulturaMontevideoUruguay
| | - Yu Shi
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Subhi Saibaba
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Ana K. Oliveira
- Department of PathologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - John R. Lukens
- Department of NeuroscienceUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Andrés Norambuena
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Joseph A. Thompson
- Department of Materials Science & EngineeringUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Michael D. Purdy
- Department of Molecular Physiology and Biological PhysicsUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Kelly Dryden
- Department of Molecular Physiology and Biological PhysicsUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - Evelyn Pardo
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - James W. Mandell
- Department of PathologyUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - George S. Bloom
- Department of BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
- Department of NeuroscienceUniversity of VirginiaCharlottesvilleVirginiaUSA
- Department of Cell BiologyUniversity of VirginiaCharlottesvilleVirginiaUSA
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2
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McIntire WE, Purdy MD, Leonhardt SA, Kucharska I, Hanson MA, Poulos S, Garrison JC, Linden J, Yeager M. G protein β 4 as a structural determinant of enhanced nucleotide exchange in the A 2AAR-Gs complex. Res Sq 2024:rs.3.rs-3814988. [PMID: 38343806 PMCID: PMC10854301 DOI: 10.21203/rs.3.rs-3814988/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Adenosine A2A receptors (A2AAR) evoke pleiotropic intracellular signaling events via activation of the stimulatory heterotrimeric G protein, Gs. Here, we used cryoEM to solve the agonist-bound structure of A2AAR in a complex with full-length Gs α and Gβ4γ2 (A2AAR-Gs α:β4γ2). The orthosteric binding site of A2AAR-Gs α:β4γ2 was similar to other structures of agonist-bound A2AAR, with or without Gs. Unexpectedly, the solvent accessible surface area within the interior of the complex was substantially larger for the complex with Gβ4 versus the closest analog, A2AAR-miniGs α:β1γ2. Consequently, there are fewer interactions between the switch II in Gs α and the Gβ4 torus. In reconstitution experiments Gβ4γ2 displayed a ten-fold higher efficiency over Gβ1γ2 in catalyzing A2AAR dependent GTPγS binding to Gs α. We propose that the less constrained switch II in A2AAR-Gs α:β4γ2 accounts for this increased efficiency. These results suggest that Gβ4 functions as a positive allosteric enhancer versus Gβ1.
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Affiliation(s)
- William E. McIntire
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, Florida 33146
| | - Michael D. Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
- Molecular Electron Microscopy Core, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Susan A. Leonhardt
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, Florida 33146
| | - Iga Kucharska
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, Florida 33146
| | - Michael A. Hanson
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, Florida 33146
| | - Sandra Poulos
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - James C. Garrison
- Department of Pharmacology, University of Virginia Health System, Charlottesville, VA 22903 Virginia 22908, USA
| | - Joel Linden
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - Mark Yeager
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, Florida 33146
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Purdy MD, Dryden K. Highlights from the University of Virginia Molecular Electron Microscopy Core. Microsc Microanal 2023; 29:951. [PMID: 37613658 DOI: 10.1093/micmic/ozad067.474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Michael D Purdy
- Molecular Electron Microscopy Core, University of Virginia School of Medicine, Charlottesville, Virginia, United States
| | - Kelly Dryden
- Molecular Electron Microscopy Core, University of Virginia School of Medicine, Charlottesville, Virginia, United States
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4
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Leonhardt SA, Purdy MD, Grover JR, Yang Z, Poulos S, McIntire WE, Tatham EA, Erramilli SK, Nosol K, Lai KK, Ding S, Lu M, Uchil PD, Finzi A, Rein A, Kossiakoff AA, Mothes W, Yeager M. Antiviral HIV-1 SERINC restriction factors disrupt virus membrane asymmetry. Nat Commun 2023; 14:4368. [PMID: 37474505 PMCID: PMC10359404 DOI: 10.1038/s41467-023-39262-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 06/06/2023] [Indexed: 07/22/2023] Open
Abstract
The host proteins SERINC3 and SERINC5 are HIV-1 restriction factors that reduce infectivity when incorporated into the viral envelope. The HIV-1 accessory protein Nef abrogates incorporation of SERINCs via binding to intracellular loop 4 (ICL4). Here, we determine cryoEM maps of full-length human SERINC3 and an ICL4 deletion construct, which reveal that hSERINC3 is comprised of two α-helical bundles connected by a ~ 40-residue, highly tilted, "crossmember" helix. The design resembles non-ATP-dependent lipid transporters. Consistently, purified hSERINCs reconstituted into proteoliposomes induce flipping of phosphatidylserine (PS), phosphatidylethanolamine and phosphatidylcholine. Furthermore, SERINC3, SERINC5 and the scramblase TMEM16F expose PS on the surface of HIV-1 and reduce infectivity, with similar results in MLV. SERINC effects in HIV-1 and MLV are counteracted by Nef and GlycoGag, respectively. Our results demonstrate that SERINCs are membrane transporters that flip lipids, resulting in a loss of membrane asymmetry that is strongly correlated with changes in Env conformation and loss of infectivity.
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Grants
- P01 AI150471 NIAID NIH HHS
- P41 GM103311 NIGMS NIH HHS
- G20 RR031199 NCRR NIH HHS
- R01 GM117372 NIGMS NIH HHS
- U54 AI170856 NIAID NIH HHS
- S10 OD018149 NIH HHS
- U24 GM129539 NIGMS NIH HHS
- S10 RR025067 NCRR NIH HHS
- This work was supported by the National Institutes of Health (NIH) grants P50 AI15046 and U54 AI170856-01 (M.Y., W.M. and A.K.K.), R01 AI154092 (M.Y.), R01 GM117372 (A.A.K.) and P01 AI150471 (W.M.)., by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research, and in part by the NIH Intramural AIDS Targeted Antiviral Program. S.D. and A.F. were supported by the CIHR grant 352417 and a Canada Research Chair. Some molecular graphics and analyses were performed with the University of California, San Francisco Chimera package. Chimera is developed by the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco (supported by the National Institute of General Medical Sciences Grant P41 GM103311).
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Affiliation(s)
- Susan A Leonhardt
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, FL, 33146, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
- Molecular Electron Microscopy Core, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Jonathan R Grover
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Ziwei Yang
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Sandra Poulos
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - William E McIntire
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, FL, 33146, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Elizabeth A Tatham
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Kamil Nosol
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Kin Kui Lai
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, P.O. Box B, Building 535, Frederick, MD, 21702, USA
| | - Shilei Ding
- Centre de Recherche du CHUM (CRCHUM), Montreal, QC, Canada
| | - Maolin Lu
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06510, USA
- Department of Cellular and Molecular Biology, University of Texas Health Science Center, Tyler, TX, USA
| | - Pradeep D Uchil
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Andrés Finzi
- Centre de Recherche du CHUM (CRCHUM), Montreal, QC, Canada
- Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC, Canada
| | - Alan Rein
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, P.O. Box B, Building 535, Frederick, MD, 21702, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Walther Mothes
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06510, USA.
| | - Mark Yeager
- The Phillip and Patricia Frost Institute for Chemistry and Molecular Science, University of Miami, Coral Gables, FL, 33146, USA.
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
- Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
- Department of Chemistry, University of Miami, Coral Gables, FL, 33146, USA.
- Department of Biochemistry and Molecular Biology, University of Miami, Miami, FL, 33136, USA.
- Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
- Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
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5
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Pak AJ, Purdy MD, Yeager M, Voth GA. Preservation of HIV-1 Gag Helical Bundle Symmetry by Bevirimat Is Central to Maturation Inhibition. J Am Chem Soc 2021; 143:19137-19148. [PMID: 34739240 DOI: 10.1021/jacs.1c08922] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The assembly and maturation of human immunodeficiency virus type 1 (HIV-1) require proteolytic cleavage of the Gag polyprotein. The rate-limiting step resides at the junction between the capsid protein CA and spacer peptide 1, which assembles as a six-helix bundle (6HB). Bevirimat (BVM), the first-in-class maturation inhibitor drug, targets the 6HB and impedes proteolytic cleavage, yet the molecular mechanisms of its activity, and relatedly, the escape mechanisms of mutant viruses, remain unclear. Here, we employed extensive molecular dynamics (MD) simulations and free energy calculations to quantitatively investigate molecular structure-activity relationships, comparing wild-type and mutant viruses in the presence and absence of BVM and inositol hexakisphosphate (IP6), an assembly cofactor. Our analysis shows that the efficacy of BVM is directly correlated with preservation of 6-fold symmetry in the 6HB, which exists as an ensemble of structural states. We identified two primary escape mechanisms, and both lead to loss of symmetry, thereby facilitating helix uncoiling to aid access of protease. Our findings also highlight specific interactions that can be targeted for improved inhibitor activity and support the use of MD simulations for future inhibitor design.
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Affiliation(s)
- Alexander J Pak
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, United States
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, United States.,Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, United States.,Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia 22908, United States.,Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, Virginia 22908, United States
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
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6
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Khan AK, Jagielnicki M, Bennett BC, Purdy MD, Yeager M. Cryo-EM structure of an open conformation of a gap junction hemichannel in lipid bilayer nanodiscs. Structure 2021; 29:1040-1047.e3. [PMID: 34129834 PMCID: PMC9616683 DOI: 10.1016/j.str.2021.05.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 02/26/2021] [Accepted: 05/14/2021] [Indexed: 12/30/2022]
Abstract
To mediate cell-to-cell communication via gap junction channels (GJCs), connexins (Cx) traffic as hexameric hemichannels to the plasma membrane, which dock end-to-end between adjacent cell membranes, thereby forming a dodecameric intercellular conduit. Hemichannels also function independently to mediate the passage of contents between the cytoplasm and extracellular space. To generate hemichannels, the mutation N176Y was introduced into the second extracellular loop of Cx26. The electron cryomicroscopy structure of the hexameric hemichannel in lipid bilayer nanodiscs displays an open pore and a 4-helix bundle transmembrane design that is nearly identical to dodecameric GJCs. In contrast to the high resolution of the transmembrane α-helices, the extracellular loops are less well resolved. The conformational flexibility of the extracellular loops may be essential to facilitate surveillance of hemichannels in apposed cells to identify compatible Cx isoforms that enable intercellular docking. Our results also provide a structural foundation for previous electrophysiologic and permeation studies of Cx hemichannels.
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Affiliation(s)
- Ali K Khan
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Maciej Jagielnicki
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Brad C Bennett
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA; Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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7
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Khan AK, Jagielnicki M, McIntire WE, Purdy MD, Dharmarajan V, Griffin PR, Yeager M. A Steric “Ball-and-Chain” Mechanism for pH-Mediated Regulation of Gap Junction Channels. Cell Rep 2020; 31:107482. [PMID: 32320665 DOI: 10.1016/j.celrep.2020.03.046] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 09/10/2019] [Accepted: 03/13/2020] [Indexed: 12/21/2022] Open
Abstract
Gap junction channels (GJCs) mediate intercellular communication and are gated by numerous conditions such as pH. The electron cryomicroscopy (cryo-EM) structure of Cx26 GJC at physiological pH recapitulates previous GJC structures in lipid bilayers. At pH 6.4, we identify two conformational states, one resembling the open physiological-pH structure and a closed conformation that displays six threads of density, that join to form a pore-occluding density. Crosslinking and hydrogen-deuterium exchange mass spectrometry reveal closer association between the N-terminal (NT) domains and the cytoplasmic loops (CL) at acidic pH. Previous electrophysiologic studies suggest an association between NT residue N14 and H100 near M2, which may trigger the observed movement of M2 toward M1 in our cryo-EM maps, thereby accounting for additional NT-CL crosslinks at acidic pH. We propose that these pH-induced interactions and conformational changes result in extension, ordering, and association of the acetylated NT domains to form a hexameric "ball-and-chain" gating particle.
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Mukherjee S, Erramilli SK, Ammirati M, Alvarez FJD, Fennell KF, Purdy MD, Skrobek BM, Radziwon K, Coukos J, Kang Y, Dutka P, Gao X, Qiu X, Yeager M, Eric Xu H, Han S, Kossiakoff AA. Synthetic antibodies against BRIL as universal fiducial marks for single-particle cryoEM structure determination of membrane proteins. Nat Commun 2020; 11:1598. [PMID: 32221310 PMCID: PMC7101349 DOI: 10.1038/s41467-020-15363-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 03/03/2020] [Indexed: 12/22/2022] Open
Abstract
We propose the concept of universal fiducials based on a set of pre-made semi-synthetic antibodies (sABs) generated by customized phage display selections against the fusion protein BRIL, an engineered variant of apocytochrome b562a. These sABs can bind to BRIL fused either into the loops or termini of different GPCRs, ion channels, receptors and transporters without disrupting their structure. A crystal structure of BRIL in complex with an affinity-matured sAB (BAG2) that bound to all systems tested delineates the footprint of interaction. Negative stain and cryoEM data of several examples of BRIL-membrane protein chimera highlight the effectiveness of the sABs as universal fiducial marks. Taken together with a cryoEM structure of sAB bound human nicotinic acetylcholine receptor, this work demonstrates that these anti-BRIL sABs can greatly enhance the particle properties leading to improved cryoEM outcomes, especially for challenging membrane proteins.
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Affiliation(s)
- Somnath Mukherjee
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Mark Ammirati
- Medicine Design, Worldwide Research and Development, Pfizer Inc., Eastern Point Road, Groton, CT, 06340, USA
| | - Frances J D Alvarez
- Medicine Design, Worldwide Research and Development, Pfizer Inc., Eastern Point Road, Groton, CT, 06340, USA
| | - Kimberly F Fennell
- Medicine Design, Worldwide Research and Development, Pfizer Inc., Eastern Point Road, Groton, CT, 06340, USA
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Blazej M Skrobek
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
- Gene Center and Department of Biochemistry, Ludwig Maximilian University of Munich, Munich, Germany
| | - Katarzyna Radziwon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
- Department of Biochemistry, University of Wisconsin Madison, Madison, WI, USA
| | - John Coukos
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Yanyong Kang
- Center for Cancer and Cell Biology, Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
- Takeda San Diego Inc., San Diego, CA, USA
| | - Przemysław Dutka
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Xiang Gao
- Center for Cancer and Cell Biology, Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
| | - Xiayang Qiu
- Medicine Design, Worldwide Research and Development, Pfizer Inc., Eastern Point Road, Groton, CT, 06340, USA
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - H Eric Xu
- Center for Cancer and Cell Biology, Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
- Key Laboratory of Receptor Research, VARI-SIMM Center, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Seungil Han
- Medicine Design, Worldwide Research and Development, Pfizer Inc., Eastern Point Road, Groton, CT, 06340, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA.
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, USA.
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9
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Han H, Schubert HL, McCullough J, Monroe N, Purdy MD, Yeager M, Sundquist WI, Hill CP. Structure of spastin bound to a glutamate-rich peptide implies a hand-over-hand mechanism of substrate translocation. J Biol Chem 2019; 295:435-443. [PMID: 31767681 DOI: 10.1074/jbc.ac119.009890] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 11/11/2019] [Indexed: 11/06/2022] Open
Abstract
Many members of the AAA+ ATPase family function as hexamers that unfold their protein substrates. These AAA unfoldases include spastin, which plays a critical role in the architecture of eukaryotic cells by driving the remodeling and severing of microtubules, which are cytoskeletal polymers of tubulin subunits. Here, we demonstrate that a human spastin binds weakly to unmodified peptides from the C-terminal segment of human tubulin α1A/B. A peptide comprising alternating glutamate and tyrosine residues binds more tightly, which is consistent with the known importance of glutamylation for spastin microtubule severing activity. A cryo-EM structure of the spastin-peptide complex at 4.2 Å resolution revealed an asymmetric hexamer in which five spastin subunits adopt a helical, spiral staircase configuration that binds the peptide within the central pore, whereas the sixth subunit of the hexamer is displaced from the peptide/substrate, as if transitioning from one end of the helix to the other. This configuration differs from a recently published structure of spastin from Drosophila melanogaster, which forms a six-subunit spiral without a transitioning subunit. Our structure resembles other recently reported AAA unfoldases, including the meiotic clade relative Vps4, and supports a model in which spastin utilizes a hand-over-hand mechanism of tubulin translocation and microtubule remodeling.
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Affiliation(s)
- Han Han
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Heidi L Schubert
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - John McCullough
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Nicole Monroe
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22908; Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, Virginia 22908; Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia 22908; Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | - Wesley I Sundquist
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112.
| | - Christopher P Hill
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112.
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10
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Marques MA, Purdy MD, Yeager M. CryoEM maps are full of potential. Curr Opin Struct Biol 2019; 58:214-223. [PMID: 31400843 DOI: 10.1016/j.sbi.2019.04.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 04/19/2019] [Accepted: 04/19/2019] [Indexed: 01/08/2023]
Abstract
Electron microscopy is based on elastic scattering due to Coulomb forces between the incident electrons and the sample; thus, electron scattering is dependent on the charge distribution in the sample. Unlike atomic scattering factors for X-rays, electron scattering factors for some atoms are strongly dependent on scattering angle, and the scattering factor for ionic oxygen is negative at low scattering angle. This phenomenon can result in a significant negative contribution to Coulomb potential maps by oxygen and can result in deviations in the positions of positive map features from atomic centers. An important factor that can also complicate the interpretation of cryoEM maps is the exquisite sensitivity of macromolecules to damage from electron irradiation, especially the carboxylates of acidic amino acids. Ideally, when compared with electron density maps derived by X-ray crystallography, Coulomb potential maps can provide additional details about the electrostatic environment and charge state of atoms. Enhancements in model building, refinement and computational simulation will be required to realize the full potential of EM-derived maps to reveal deeper insight into the electronic structure and functional properties of macromolecular complexes and their interactions with binding partners, ligands, cofactors, and drugs.
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Affiliation(s)
- Mayra A Marques
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Programa de Biologia Estrutural, Instituto de Bioquímica Médica Leopoldo de Meis, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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Khan AK, Jagielnicki MJ, Purdy MD, Yeager M. PH-Gating of GAP Junction Channels: Visualization of a “Ball-and-Chain” by Cryo-EM. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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12
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Wagner JM, Zadrozny KK, Chrustowicz J, Purdy MD, Yeager M, Ganser-Pornillos BK, Pornillos O. Crystal structure of an HIV assembly and maturation switch. eLife 2016; 5. [PMID: 27416583 PMCID: PMC4946879 DOI: 10.7554/elife.17063] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 06/13/2016] [Indexed: 12/25/2022] Open
Abstract
Virus assembly and maturation proceed through the programmed operation of molecular switches, which trigger both local and global structural rearrangements to produce infectious particles. HIV-1 contains an assembly and maturation switch that spans the C-terminal domain (CTD) of the capsid (CA) region and the first spacer peptide (SP1) of the precursor structural protein, Gag. The crystal structure of the CTD-SP1 Gag fragment is a goblet-shaped hexamer in which the cup comprises the CTD and an ensuing type II β-turn, and the stem comprises a 6-helix bundle. The β-turn is critical for immature virus assembly and the 6-helix bundle regulates proteolysis during maturation. This bipartite character explains why the SP1 spacer is a critical element of HIV-1 Gag but is not a universal property of retroviruses. Our results also indicate that HIV-1 maturation inhibitors suppress unfolding of the CA-SP1 junction and thereby delay access of the viral protease to its substrate. DOI:http://dx.doi.org/10.7554/eLife.17063.001 Viruses like HIV must undergo a process called maturation in order to successfully infect cells. Maturation involves a dramatic rearrangement in the architecture of the virus. That is to say, the virus’s internal protein coat – called the capsid – must change from an immature sphere into a mature cone-shaped coat. Notably, this maturation process is what is disrupted by the protease inhibitors that are a major component of anti-HIV drug cocktails. Structural changes in small portions of the capsid protein, termed molecular switches, commonly trigger the viral capsids to reorganize. The HIV capsid has two of these switches, and Wagner, Zadrozny et al. set out to understand how one of them – called the CA-SP1 switch – works. Solving the three-dimensional structure of the immature form of the CA-SP1 switch revealed that it forms a well-structured bundle of six helices. This helical bundle captures another section of the capsid protein that would otherwise be cut by a viral protease. The CA-SP1 switch therefore controls how quickly the protein is cut and the start of the maturation process. Wagner, Zadrozny et al. then discovered that other small molecule inhibitors of HIV, called maturation inhibitors, work by binding to and disrupting the transformation of the CA-SP1 switch. Finally, further experiments showed that the formation of the CA-SP1 helical bundle controls when the immature capsid shell forms and coordinates the process with the capsid gaining the genetic material of the virus. The new structure means that researchers now know what the HIV capsid looks like at the start and end of maturation. The next challenge will be to figure out exactly how the capsid changes from one form to the next as HIV matures. DOI:http://dx.doi.org/10.7554/eLife.17063.002
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Affiliation(s)
- Jonathan M Wagner
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Kaneil K Zadrozny
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Jakub Chrustowicz
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States.,Department of Medicine, Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, United States
| | - Barbie K Ganser-Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
| | - Owen Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, United States
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Purdy MD, Bennett BC, McIntire WE, Khan AK, Kasson PM, Yeager M. Function and dynamics of macromolecular complexes explored by integrative structural and computational biology. Curr Opin Struct Biol 2014; 27:138-48. [PMID: 25238653 PMCID: PMC6387792 DOI: 10.1016/j.sbi.2014.08.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 08/12/2014] [Indexed: 12/22/2022]
Abstract
Three vignettes exemplify the potential of combining EM and X-ray crystallographic data with molecular dynamics (MD) simulation to explore the architecture, dynamics and functional properties of multicomponent, macromolecular complexes. The first two describe how EM and X-ray crystallography were used to solve structures of the ribosome and the Arp2/3-actin complex, which enabled MD simulations that elucidated functional dynamics. The third describes how EM, X-ray crystallography, and microsecond MD simulations of a GPCR:G protein complex were used to explore transmembrane signaling by the β-adrenergic receptor. Recent technical advancements in EM, X-ray crystallography and computational simulation create unprecedented synergies for integrative structural biology to reveal new insights into heretofore intractable biological systems.
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Affiliation(s)
- Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Brad C Bennett
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - William E McIntire
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Ali K Khan
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Peter M Kasson
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Biomedical Engineering, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Vergis JM, Purdy MD, Wiener MC. A high-throughput differential filtration assay to screen and select detergents for membrane proteins. Anal Biochem 2010; 407:1-11. [PMID: 20667442 DOI: 10.1016/j.ab.2010.07.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 07/19/2010] [Accepted: 07/20/2010] [Indexed: 10/19/2022]
Abstract
Structural studies on integral membrane proteins are routinely performed on protein-detergent complexes (PDCs) consisting of purified protein solubilized in a particular detergent. Of all the membrane protein crystal structures solved to date, a subset of only four detergents has been used in more than half of these structures. Unfortunately, many membrane proteins are not well behaved in these four detergents and/or fail to yield well-diffracting crystals. Identification of detergents that maintain the solubility and stability of a membrane protein is a critical step and can be a lengthy and "protein-expensive" process. We have developed an assay that characterizes the stability and size of membrane proteins exchanged into a panel of 94 commercially available and chemically diverse detergents. This differential filtration assay (DFA), using a set of filtered microplates, requires sub-milligram quantities of purified protein and small quantities of detergents and other reagents and is performed in its entirety in several hours.
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Affiliation(s)
- James M Vergis
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
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Cuello LG, Jogini V, Cortes DM, Sompornpisut A, Purdy MD, Wiener MC, Perozo E. Design and characterization of a constitutively open KcsA. FEBS Lett 2010; 584:1133-8. [PMID: 20153331 DOI: 10.1016/j.febslet.2010.02.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2009] [Revised: 02/01/2010] [Accepted: 02/01/2010] [Indexed: 11/16/2022]
Abstract
The molecular nature of the structure responsible for proton sensitivity in KcsA has been identified as a charge cluster that surrounds the inner helical bundle gate. Here, we show that this proton sensor can be modified to engineer a constitutively open form of KcsA, amenable to functional, spectroscopic and structural analyses. By combining charge neutralizations for all acidic and basic residues in the cluster at positions 25, 117-122 and 124 (but not E118), a mutant KcsA is generated that displays constitutively open channel activity up to pH 9. The structure of this mutant revealed that full opening appears to be inhibited by lattice forces since the activation gate seems to be only on the early stages of opening.
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Affiliation(s)
- Luis G Cuello
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
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Shultis DD, Purdy MD, Banchs CN, Wiener MC. Crystallization and preliminary X-ray crystallographic analysis of the Escherichia coli outer membrane cobalamin transporter BtuB in complex with the carboxy-terminal domain of TonB. Acta Crystallogr Sect F Struct Biol Cryst Commun 2006; 62:638-41. [PMID: 16820681 PMCID: PMC2242962 DOI: 10.1107/s1744309106018240] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 05/16/2006] [Indexed: 11/10/2022]
Abstract
The energy-dependent uptake of organometallic compounds and other micronutrients across the outer membranes of Gram-negative bacteria is carried out by outer membrane active-transport proteins that utilize the proton-motive force of the inner membrane via coupling to the TonB protein. The Escherichia coli outer membrane cobalamin transporter BtuB and a carboxy-terminal domain of the TonB protein, residues 147-239 of the wild-type protein, were expressed and purified individually. A complex of BtuB and TonB(147-239) was formed in the presence of the substrate cyanocobalamin (CN-Cbl; vitamin B12) and calcium and was crystallized. BtuB was purified in the detergent LDAO (n-dodecyl-N,N-dimethylamine-N-oxide) and the complex was formed in a detergent mixture of LDAO and C8E4 (tetraethylene glycol monooctylether). Crystals were obtained by sitting-drop vapor diffusion, with the reservoir containing 30%(v/v) polyethylene glycol (PEG 300) and 100 mM sodium acetate pH 5.2. The crystals belong to space group P2(1)2(1)2(1) (unit-cell parameters a = 74.3, b = 82.4, c = 122.6 angstroms). The asymmetric unit consists of a single BtuB-TonB complex. Data sets have been collected to 2.1 angstroms resolution at a synchrotron beamline (APS SER-CAT 22-ID).
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Affiliation(s)
- David D. Shultis
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA
| | - Michael D. Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA
| | - Christian N. Banchs
- Interdisciplinary Graduate Program in Biophysics, University of Virginia, Charlottesville, Virginia 22908, USA
| | - Michael C. Wiener
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA
- Interdisciplinary Graduate Program in Biophysics, University of Virginia, Charlottesville, Virginia 22908, USA
- Correspondence e-mail:
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Abstract
In Gram-negative bacteria, the import of essential micronutrients across the outer membrane requires a transporter, an electrochemical gradient of protons across the inner membrane, and an inner membrane protein complex (ExbB, ExbD, TonB) that couples the proton-motive force to the outer membrane transporter. The inner membrane protein TonB binds directly to a conserved region, called the Ton-box, of the transporter. We solved the structure of the cobalamin transporter BtuB in complex with the C-terminal domain of TonB. In contrast to its conformations in the absence of TonB, the Ton-box forms a beta strand that is recruited to the existing beta sheet of TonB, which is consistent with a mechanical pulling model of transport.
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Affiliation(s)
- David D Shultis
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
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Purdy MD, Ge P, Chen J, Selvin PR, Wiener MC. Thiol-reactive lanthanide chelates for phasing protein X-ray diffraction data. Acta Crystallogr D Biol Crystallogr 2002; 58:1111-7. [PMID: 12077430 DOI: 10.1107/s0907444902006509] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2002] [Accepted: 04/11/2002] [Indexed: 02/25/2023]
Abstract
Lanthanides can contribute a large anomalous component to X-ray scattering when present and ordered in a target crystal. This large anomalous signal is a useful source of phase information in X-ray crystallographic studies of biological macromolecules. Thiol-reactive lanthanide chelates were tested as a means of incorporation of lanthanides into protein crystals. Two compounds, each capable of being loaded with a lanthanide of choice, were synthesized: diethylenetriaminepentaacetic 3-(2-pyridyldithio)propionyl hydrazide (DTPA-PDPH) and 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic 3-(2-pyridyldithio)propionyl hydrazide (DOTA-PDPH). A cysteine mutant of the 34 kDa phosphate-binding protein (PBP-A197C) from Escherichia coli was used as a test case. PBP-A197C was labeled with DTPA-PDPH loaded with dysprosium. Characteristics of DTPA-PDPH enabled spectroscopic monitoring of the labeling reaction. Complete labeling of PBP-A197C was confirmed by mass spectrometry and SDS-PAGE analysis. Labeled PBP-A197C (PBP-A197C-DTPA-Dy) crystallized identically to unlabeled protein. X-ray diffraction data were collected from PBP-A197C-DTPA-Dy crystals in-house with a Cu Kalpha rotating-anode source and with a tuneable synchrotron source (ALS 5.0.2). Synchrotron data were collected at energies corresponding to the Dy L(III) edge f" peak and a high-energy remote. Each data set was treated as an independent SAD experiment. A large anomalous signal was present in the data collected in-house and at the synchrotron. The Dy site was easily located in anomalous difference Patterson maps calculated from each of the data sets. In each case, SAD phasing resulted in high-quality electron-density maps, as evidenced by the success of automated model building. The generality of the method was analyzed with several other test proteins. Labeling of some of these proteins with thiol-reactive lanthanide chelates was deleterious to protein solubility or crystallization. In two of the cases the lanthanide chelate was disordered in the crystals. These results suggest that this method may not be well suited for high-throughput crystallography. However, for difficult cases requiring a large anomalous signal, thiol-reactive lanthanide chelates may prove to be a valuable tool.
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Affiliation(s)
- Michael D Purdy
- Interdisciplinary Program in Biophysics, University of Virginia, 1300 Jefferson Park Avenue, Charlottesville 22908, USA
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Snook CF, Purdy MD, Wiener MC. Use of a crystallization robot to set up sitting-drop vapor-diffusion crystallization andin situcrystallization screens. J Appl Crystallogr 2000. [DOI: 10.1107/s0021889800001151] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
A commercial crystallization robot has been modified for use in setting up sitting-drop vapor-diffusion crystallization experiments, and for setting up protein crystallization screensin situ. The primary aim of this effort is the automated screening of crystallization of integral membrane proteins in detergent-containing solutions. However, the results of this work are of general utility to robotic liquid-handling systems. Sources of error that can prevent the accurate dispensing and mixing of solutions have been identified, and include local environmental, machine-specific and solution conditions. Solutions to each of these problems have been developed and implemented.
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Abstract
YadQ of Escherichia coli is a homolog of the mammalian chloride channels of the ClC family. The yadQ gene was cloned as a fusion protein with a hexahistidine tag and tobacco etch virus protease site for the removal of the tag. The protein was expressed in the membrane of E. coli and extracted with decylmaltoside. Purification was achieved by metal affinity chromatography followed by cation exchange. Circular dichroism revealed a high alpha-helical content. Size exclusion chromatography suggests that YadQ forms dimers. The similarity in primary, secondary, and quaternary structure and the ability to recombinantly express YadQ in the cell membrane make the protein a good candidate for the structural study of ClC chloride channels.
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Affiliation(s)
- M D Purdy
- Biophysics Program, University of Virginia, 1300 Jefferson Park Ave, Charlottesville, VA 22906-0011, USA
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