451
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Merk A, Bartesaghi A, Banerjee S, Falconieri V, Rao P, Davis MI, Pragani R, Boxer MB, Earl LA, Milne JLS, Subramaniam S. Breaking Cryo-EM Resolution Barriers to Facilitate Drug Discovery. Cell 2016; 165:1698-1707. [PMID: 27238019 DOI: 10.1016/j.cell.2016.05.040] [Citation(s) in RCA: 331] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 05/09/2016] [Accepted: 05/09/2016] [Indexed: 11/17/2022]
Abstract
Recent advances in single-particle cryoelecton microscopy (cryo-EM) are enabling generation of numerous near-atomic resolution structures for well-ordered protein complexes with sizes ≥ ∼200 kDa. Whether cryo-EM methods are equally useful for high-resolution structural analysis of smaller, dynamic protein complexes such as those involved in cellular metabolism remains an important question. Here, we present 3.8 Å resolution cryo-EM structures of the cancer target isocitrate dehydrogenase (93 kDa) and identify the nature of conformational changes induced by binding of the allosteric small-molecule inhibitor ML309. We also report 2.8-Å- and 1.8-Å-resolution structures of lactate dehydrogenase (145 kDa) and glutamate dehydrogenase (334 kDa), respectively. With these results, two perceived barriers in single-particle cryo-EM are overcome: (1) crossing 2 Å resolution and (2) obtaining structures of proteins with sizes < 100 kDa, demonstrating that cryo-EM can be used to investigate a broad spectrum of drug-target interactions and dynamic conformational states.
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Affiliation(s)
- Alan Merk
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Alberto Bartesaghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Soojay Banerjee
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Veronica Falconieri
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Prashant Rao
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Mindy I Davis
- National Center for Advancing Translational Sciences, 9800 Medical Center Drive, Rockville, MD 20850, USA
| | - Rajan Pragani
- National Center for Advancing Translational Sciences, 9800 Medical Center Drive, Rockville, MD 20850, USA
| | - Matthew B Boxer
- National Center for Advancing Translational Sciences, 9800 Medical Center Drive, Rockville, MD 20850, USA
| | - Lesley A Earl
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Jacqueline L S Milne
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Sriram Subramaniam
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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452
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Fukumori A, Steiner H. Substrate recruitment of γ-secretase and mechanism of clinical presenilin mutations revealed by photoaffinity mapping. EMBO J 2016; 35:1628-43. [PMID: 27220847 DOI: 10.15252/embj.201694151] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/26/2016] [Indexed: 12/27/2022] Open
Abstract
Intramembrane proteases execute fundamental biological processes ranging from crucial signaling events to general membrane proteostasis. Despite the availability of structural information on these proteases, it remains unclear how these enzymes bind and recruit substrates, particularly for the Alzheimer's disease-associated γ-secretase. Systematically scanning amyloid precursor protein substrates containing a genetically inserted photocrosslinkable amino acid for binding to γ-secretase allowed us to identify residues contacting the protease. These were primarily found in the transmembrane cleavage domain of the substrate and were also present in the extramembranous domains. The N-terminal fragment of the catalytic subunit presenilin was determined as principal substrate-binding site. Clinical presenilin mutations altered substrate binding in the active site region, implying a pathogenic mechanism for familial Alzheimer's disease. Remarkably, PEN-2 was identified besides nicastrin as additional substrate-binding subunit. Probing proteolysis of crosslinked substrates revealed a mechanistic model of how these subunits interact to mediate a stepwise transfer of bound substrate to the catalytic site. We propose that sequential binding steps might be common for intramembrane proteases to sample and select cognate substrates for catalysis.
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Affiliation(s)
- Akio Fukumori
- Biomedical Center (BMC), Metabolic Biochemistry, Ludwig-Maximilians-University Munich, Munich, Germany German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Harald Steiner
- Biomedical Center (BMC), Metabolic Biochemistry, Ludwig-Maximilians-University Munich, Munich, Germany German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
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453
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Voorhees RM, Hegde RS. Toward a structural understanding of co-translational protein translocation. Curr Opin Cell Biol 2016; 41:91-9. [PMID: 27155805 DOI: 10.1016/j.ceb.2016.04.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 04/22/2016] [Accepted: 04/25/2016] [Indexed: 01/06/2023]
Abstract
The translocation of most eukaryotic secreted and integral membrane proteins occurs co-translationally at the endoplasmic reticulum (ER). These nascent polypeptides are recognized on the ribosome by the signal recognition particle (SRP), targeted to the ER, and translocated across or inserted into the membrane by the Sec61 translocation channel. Structural analysis of these co-translational processes has been challenging due to the size, complexity, and flexibility of the targeting and translocation machinery. Recent technological advances in cryo-electron microscopy (cryo-EM) have resulted in increasingly powerful tools to study large, heterogeneous, and low-abundance samples. These advances are being utilized to obtain near-atomic resolution reconstructions of functional translation, targeting, and translocation intermediates, paving the way to a mechanistic understanding of protein biogenesis.
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Affiliation(s)
- Rebecca M Voorhees
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom.
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454
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Baretić D, Berndt A, Ohashi Y, Johnson CM, Williams RL. Tor forms a dimer through an N-terminal helical solenoid with a complex topology. Nat Commun 2016; 7:11016. [PMID: 27072897 PMCID: PMC4833857 DOI: 10.1038/ncomms11016] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 02/11/2016] [Indexed: 01/18/2023] Open
Abstract
The target of rapamycin (Tor) is a Ser/Thr protein kinase that regulates a range of anabolic and catabolic processes. Tor is present in two complexes, TORC1 and TORC2, in which the Tor–Lst8 heterodimer forms a common sub-complex. We have determined the cryo-electron microscopy (EM) structure of Tor bound to Lst8. Two Tor–Lst8 heterodimers assemble further into a dyad-symmetry dimer mediated by Tor–Tor interactions. The first 1,300 residues of Tor form a HEAT repeat-containing α-solenoid with four distinct segments: a highly curved 800-residue N-terminal 'spiral', followed by a 400-residue low-curvature 'bridge' and an extended ‘railing' running along the bridge leading to the 'cap' that links to FAT region. This complex topology was verified by domain insertions and offers a new interpretation of the mTORC1 structure. The spiral of one TOR interacts with the bridge of another, which together form a joint platform for the Regulatory Associated Protein of TOR (RAPTOR) regulatory subunit. The target of rapamycin (Tor) is a Ser/Thr protein kinase that regulates a wide range of anabolic and catabolic processes. Here the authors describe a sub-nanometer cryo-EM structure of a yeast Tor–Lst8 complex and propose an overall topology that differs from that previously suggested for mTORC1.
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Affiliation(s)
| | - Alex Berndt
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Yohei Ohashi
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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455
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Structure of the full-length TRPV2 channel by cryo-EM. Nat Commun 2016; 7:11130. [PMID: 27021073 PMCID: PMC4820614 DOI: 10.1038/ncomms11130] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 02/23/2016] [Indexed: 12/12/2022] Open
Abstract
Transient receptor potential (TRP) proteins form a superfamily Ca2+-permeable cation channels regulated by a range of chemical and physical stimuli. Structural analysis of a ‘minimal' TRP vanilloid subtype 1 (TRPV1) elucidated a mechanism of channel activation by agonists through changes in its outer pore region. Though homologous to TRPV1, other TRPV channels (TRPV2–6) are insensitive to TRPV1 activators including heat and vanilloids. To further understand the structural basis of TRPV channel function, we determined the structure of full-length TRPV2 at ∼5 Å resolution by cryo-electron microscopy. Like TRPV1, TRPV2 contains two constrictions, one each in the pore-forming upper and lower gates. The agonist-free full-length TRPV2 has wider upper and lower gates compared with closed and agonist-activated TRPV1. We propose these newly revealed TRPV2 structural features contribute to diversity of TRPV channels. Transient receptor potential (TRP) proteins are Ca2+-permeable cation channels activated by a range of chemical and physical stimuli. Here the authors describe a cryo-EM structure of the full-length TRPV2 channel that provides insight into the regulation of the TRPV subfamily of channels.
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456
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Rawson S, Davies S, Lippiat JD, Muench SP. The changing landscape of membrane protein structural biology through developments in electron microscopy. Mol Membr Biol 2016; 33:12-22. [PMID: 27608730 PMCID: PMC5206964 DOI: 10.1080/09687688.2016.1221533] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 07/14/2016] [Accepted: 07/19/2016] [Indexed: 11/30/2022]
Abstract
Membrane proteins are ubiquitous in biology and are key targets for therapeutic development. Despite this, our structural understanding has lagged behind that of their soluble counterparts. This review provides an overview of this important field, focusing in particular on the recent resurgence of electron microscopy (EM) and the increasing role it has to play in the structural studies of membrane proteins, and illustrating this through several case studies. In addition, we examine some of the challenges remaining in structural determination, and what steps are underway to enhance our knowledge of these enigmatic proteins.
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Affiliation(s)
- Shaun Rawson
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds,
Leeds,
UK
| | - Simon Davies
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds,
Leeds,
UK
| | - Jonathan D. Lippiat
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds,
Leeds,
UK
| | - Stephen P. Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds,
Leeds,
UK
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457
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Nguyen THD, Galej WP, Bai XC, Oubridge C, Newman AJ, Scheres SHW, Nagai K. Cryo-EM structure of the yeast U4/U6.U5 tri-snRNP at 3.7 Å resolution. Nature 2016; 530:298-302. [PMID: 26829225 PMCID: PMC4762201 DOI: 10.1038/nature16940] [Citation(s) in RCA: 162] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 12/18/2015] [Indexed: 12/12/2022]
Abstract
U4/U6.U5 tri-snRNP represents a substantial part of the spliceosome before activation. A cryoEM structure of Saccharomyces cerevisiae U4/U6.U5 tri-snRNP at 3.7Å resolution led to an essentially complete atomic model comprising 30 proteins plus U4/U6 and U5 snRNAs. The structure reveals striking interweaving interactions of the protein and RNA components including extended polypeptides penetrating into subunit interfaces. The invariant ACAGAGA sequence of U6 snRNA, which base-pairs with the 5′-splice site during catalytic activation, forms a hairpin stabilised by Dib1 and Prp8 while the adjacent nucleotides interact with the exon binding loop 1 of U5 snRNA. Snu114 harbours GTP but its putative catalytic histidine is held away from the γ-phosphate by hydrogen bonding to a tyrosine in Prp8’s N-terminal domain. Mutation of this histidine to alanine has no detectable effect on yeast growth. The structure provides important new insights into the spliceosome activation process leading to the formation of the catalytic centre.
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Affiliation(s)
| | - Wojciech P Galej
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Xiao-Chen Bai
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Chris Oubridge
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Andrew J Newman
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Sjors H W Scheres
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
| | - Kiyoshi Nagai
- MRC Laboratory of Molecular Biology Francis Crick Avenue Cambridge CB2 0QH UK
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458
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Tan YZ, Cheng A, Potter CS, Carragher B. Automated data collection in single particle electron microscopy. Microscopy (Oxf) 2015; 65:43-56. [PMID: 26671944 DOI: 10.1093/jmicro/dfv369] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 11/06/2015] [Indexed: 11/12/2022] Open
Abstract
Automated data collection is an integral part of modern workflows in single particle electron microscopy (EM) research. This review surveys the software packages available for automated single particle EM data collection. The degree of automation at each stage of data collection is evaluated, and the capabilities of the software packages are described. Finally, future trends in automation are discussed.
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Affiliation(s)
- Yong Zi Tan
- The National Resource for Automated Molecular Microscopy, New York Structural Biology Center, New York, NY 10027, USA Simons Electron Microscopy Center, New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, USA Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Anchi Cheng
- The National Resource for Automated Molecular Microscopy, New York Structural Biology Center, New York, NY 10027, USA Simons Electron Microscopy Center, New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, USA
| | - Clinton S Potter
- The National Resource for Automated Molecular Microscopy, New York Structural Biology Center, New York, NY 10027, USA Simons Electron Microscopy Center, New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, USA Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Bridget Carragher
- The National Resource for Automated Molecular Microscopy, New York Structural Biology Center, New York, NY 10027, USA Simons Electron Microscopy Center, New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, USA Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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