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Peters MH, Bastidas O, Kokron DS, Henze CE. Transformations, Lineage Comparisons, and Analysis of Down to Up Protomer States of Variants of the SARS-CoV-2 Prefusion Spike Protein Including the UK Variant B.1.1.7. bioRxiv 2021. [PMID: 33594365 DOI: 10.1101/2021.02.09.430519] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Monitoring and strategic response to variants in SARS-CoV-2 represents a considerable challenge in the current pandemic, as well as potentially future viral outbreaks of similar magnitude. In particular mutations and deletions involving the virion's prefusion Spike protein have significant potential impact on vaccines and therapeutics that utilize this key structural viral protein in their mitigation strategies. In this study, we have demonstrated how dominant energetic landscape mappings ("glue points") coupled with sequence alignment information can potentially identify or flag key residue mutations and deletions associated with variants. Surprisingly, we also found excellent homology of stabilizing residue glue points across the lineage of β coronavirus Spike proteins, and we have termed this as "sequence homologous glue points". In general, these flagged residue mutations and/or deletions are then computationally studied in detail using all-atom biocomputational molecular dynamics over approximately one microsecond in order to ascertain structural and energetic changes in the Spike protein associated variants. Specifically, we examined both a theoretically-based triple mutant and the so-called UK or B.1.1.7 variant. For the theoretical triple mutant, we demonstrated through Alanine mutations, which help "unglue" key residue-residue interactions, that these three key stabilizing residues could cause the transition of Down to Up protomer states, where the Up protomer state allows binding of the prefusion Spike protein to hACE2 host cell receptors, whereas the Down state is believed inaccessible. Thus, we are able to demonstrate the importance of glue point residue identification in the overall stability of the prefusion Spike protein. For the B.1.1.7 variant, we demonstrated the critical importance of D614G and N5017 on the structure and binding, respectively, of the Spike protein. Notably, we had previously identified D614 as a key glue point in the inter-protomer stabilization of the Spike protein prior to the emergence of its mutation. The mutant D614G is a structure breaking Glycine mutation demonstrating a relatively more distal Down state RBD and a more stable conformation in general. In addition, we demonstrate that the mutation N501Y may significantly increase the Spike protein binding to hACE2 cell receptors through its interaction with Y41 of hACE2 forming a potentially strong hydrophobic residue binding pair. We note that these two key mutations, D614G and N501Y, are also found in the so-called South African (SA; B.1.351) variant of SARS-CoV-2. Future studies along these lines are, therefore, aimed at mapping glue points to residue mutations and deletions of associated prefusion Spike protein variants in order to help identify and analyze possible "variants of interest" and optimize efforts aimed at the mitigation of this current and future virions.
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2
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Trifonov T, Caballero JA, Morales JC, Seifahrt A, Ribas I, Reiners A, Bean JL, Luque R, Parviainen H, Pallé E, Stock S, Zechmeister M, Amado PJ, Anglada-Escudé G, Azzaro M, Barclay T, Béjar VJS, Bluhm P, Casasayas-Barris N, Cifuentes C, Collins KA, Collins KI, Cortés-Contreras M, de Leon J, Dreizler S, Dressing CD, Esparza-Borges E, Espinoza N, Fausnaugh M, Fukui A, Hatzes AP, Hellier C, Henning T, Henze CE, Herrero E, Jeffers SV, Jenkins JM, Jensen ELN, Kaminski A, Kasper D, Kossakowski D, Kürster M, Lafarga M, Latham DW, Mann AW, Molaverdikhani K, Montes D, Montet BT, Murgas F, Narita N, Oshagh M, Passegger VM, Pollacco D, Quinn SN, Quirrenbach A, Ricker GR, Rodríguez López C, Sanz-Forcada J, Schwarz RP, Schweitzer A, Seager S, Shporer A, Stangret M, Stürmer J, Tan TG, Tenenbaum P, Twicken JD, Vanderspek R, Winn JN. A nearby transiting rocky exoplanet that is suitable for atmospheric investigation. Science 2021; 371:1038-1041. [PMID: 33674491 DOI: 10.1126/science.abd7645] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 02/02/2021] [Indexed: 11/02/2022]
Abstract
Spectroscopy of transiting exoplanets can be used to investigate their atmospheric properties and habitability. Combining radial velocity (RV) and transit data provides additional information on exoplanet physical properties. We detect a transiting rocky planet with an orbital period of 1.467 days around the nearby red dwarf star Gliese 486. The planet Gliese 486 b is 2.81 Earth masses and 1.31 Earth radii, with uncertainties of 5%, as determined from RV data and photometric light curves. The host star is at a distance of ~8.1 parsecs, has a J-band magnitude of ~7.2, and is observable from both hemispheres of Earth. On the basis of these properties and the planet's short orbital period and high equilibrium temperature, we show that this terrestrial planet is suitable for emission and transit spectroscopy.
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Affiliation(s)
- T Trifonov
- Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany.
| | - J A Caballero
- Centro de Astrobiología (Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial), E-28692 Villanueva de la Cañada, Madrid, Spain
| | - J C Morales
- Institut de Ciències de l'Espai (Consejo Superior de Investigaciones Científicas), E-08193 Bellaterra, Barcelona, Spain.,Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona, Spain
| | - A Seifahrt
- Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
| | - I Ribas
- Institut de Ciències de l'Espai (Consejo Superior de Investigaciones Científicas), E-08193 Bellaterra, Barcelona, Spain.,Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona, Spain
| | - A Reiners
- Institut für Astrophysik, Georg-August-Universität, D-37077 Göttingen, Germany
| | - J L Bean
- Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
| | - R Luque
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - H Parviainen
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - E Pallé
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - S Stock
- Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, D-69117 Heidelberg, Germany
| | - M Zechmeister
- Institut für Astrophysik, Georg-August-Universität, D-37077 Göttingen, Germany
| | - P J Amado
- Instituto de Astrofísica de Andalucía (Consejo Superior de Investigaciones Científicas), E-18008 Granada, Spain
| | - G Anglada-Escudé
- Institut de Ciències de l'Espai (Consejo Superior de Investigaciones Científicas), E-08193 Bellaterra, Barcelona, Spain.,Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona, Spain
| | - M Azzaro
- Centro Astronómico Hispano-Alemán, Observatorio de Calar Alto, E-04550 Gérgal, Almería, Spain
| | - T Barclay
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.,University of Maryland, Baltimore County, Baltimore, MD 21250, USA
| | - V J S Béjar
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - P Bluhm
- Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, D-69117 Heidelberg, Germany
| | - N Casasayas-Barris
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - C Cifuentes
- Centro de Astrobiología (Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial), E-28692 Villanueva de la Cañada, Madrid, Spain
| | - K A Collins
- Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA 02138, USA
| | - K I Collins
- Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, USA
| | - M Cortés-Contreras
- Centro de Astrobiología (Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial), E-28692 Villanueva de la Cañada, Madrid, Spain
| | - J de Leon
- Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - S Dreizler
- Institut für Astrophysik, Georg-August-Universität, D-37077 Göttingen, Germany
| | - C D Dressing
- Astronomy Department, University of California at Berkeley, Berkeley, CA 94720, USA
| | - E Esparza-Borges
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - N Espinoza
- Space Telescope Science Institute, Baltimore, MD 21218, USA
| | - M Fausnaugh
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - A Fukui
- Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan.,Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
| | - A P Hatzes
- Thüringer Landessternwarte Tautenburg, D-07778 Tautenburg, Germany
| | - C Hellier
- Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
| | - Th Henning
- Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany
| | - C E Henze
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - E Herrero
- Institut de Ciències de l'Espai (Consejo Superior de Investigaciones Científicas), E-08193 Bellaterra, Barcelona, Spain.,Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona, Spain
| | - S V Jeffers
- Institut für Astrophysik, Georg-August-Universität, D-37077 Göttingen, Germany.,Max-Planck-Institut für Sonnensystemforschung, D-37077, Göttingen, Germany
| | - J M Jenkins
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - E L N Jensen
- Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081, USA
| | - A Kaminski
- Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, D-69117 Heidelberg, Germany
| | - D Kasper
- Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
| | - D Kossakowski
- Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany
| | - M Kürster
- Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany
| | - M Lafarga
- Institut de Ciències de l'Espai (Consejo Superior de Investigaciones Científicas), E-08193 Bellaterra, Barcelona, Spain.,Institut d'Estudis Espacials de Catalunya, E-08034 Barcelona, Spain
| | - D W Latham
- Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA 02138, USA
| | - A W Mann
- Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - K Molaverdikhani
- Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, D-69117 Heidelberg, Germany
| | - D Montes
- Departamento de Física de la Tierra y Astrofísica and Instituto de Física de Partículas y del Cosmos, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain
| | - B T Montet
- School of Physics, University of New South Wales, Sydney NSW 2052, Australia
| | - F Murgas
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - N Narita
- Komaba Institute for Science, University of Tokyo, Tokyo 153-8902, Japan.,Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology, Tokyo 153-8902, Japan.,Astrobiology Center, Tokyo 181-8588, Japan.,Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
| | - M Oshagh
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - V M Passegger
- Hamburger Sternwarte, Universität Hamburg, D-21029 Hamburg, Germany.,Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA
| | - D Pollacco
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - S N Quinn
- Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA 02138, USA
| | - A Quirrenbach
- Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, D-69117 Heidelberg, Germany
| | - G R Ricker
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - C Rodríguez López
- Instituto de Astrofísica de Andalucía (Consejo Superior de Investigaciones Científicas), E-18008 Granada, Spain
| | - J Sanz-Forcada
- Centro de Astrobiología (Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial), E-28692 Villanueva de la Cañada, Madrid, Spain
| | - R P Schwarz
- Patashnick Voorheesville Observatory, Voorheesville, NY 12186, USA
| | - A Schweitzer
- Hamburger Sternwarte, Universität Hamburg, D-21029 Hamburg, Germany
| | - S Seager
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - A Shporer
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - M Stangret
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.,Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
| | - J Stürmer
- Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, D-69117 Heidelberg, Germany
| | - T G Tan
- Perth Exoplanet Survey Telescope, Perth WA 6010, Australia
| | - P Tenenbaum
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J D Twicken
- Search for Extraterrestrial Intelligence Institute, Mountain View, CA 94043, USA.,NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - R Vanderspek
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J N Winn
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
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3
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Peters MH, Bastidas O, Kokron DS, Henze CE. Static all-atom energetic mappings of the SARS-Cov-2 spike protein and dynamic stability analysis of "Up" versus "Down" protomer states. PLoS One 2020; 15:e0241168. [PMID: 33170884 PMCID: PMC7654774 DOI: 10.1371/journal.pone.0241168] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 10/10/2020] [Indexed: 11/23/2022] Open
Abstract
The SARS-CoV-2 virion responsible for the current world-wide pandemic COVID-19 has a characteristic Spike protein (S) on its surface that embellishes both a prefusion state and fusion state. The prefusion Spike protein (S) is a large trimeric protein where each protomer may be in a so-called Up state or Down state, depending on the configuration of its receptor binding domain (RBD) within its distal, prefusion S1 domain. The Up state is believed to allow binding of the virion to ACE-2 receptors on human epithelial cells, whereas the Down state is believed to be relatively inactive or reduced in its binding behavior. We have performed detailed all-atom, dominant energy landscape mappings for noncovalent interactions (charge, partial charge, and van der Waals) of the SARS-CoV-2 Spike protein in its static prefusion state based on two recent and independent experimental structure publications. We included both interchain interactions and intrachain (domain) interactions in our mappings in order to determine any telling differences (different so-called “glue” points) between residues in the Up and Down state protomers. The S2 proximal, fusion domain demonstrated no appreciable energetic differences between Up and Down protomers, including interchain as well as each protomer’s intrachain, S1-S2 interactions. However, the S1 domain interactions across neighboring protomers, which include the RBD-NTD cross chain interactions, showed significant energetic differences between Up-Down and Down-Down neighboring protomers. This included, for example, a key RBD residue ARG357 in the Up-Down interaction and a three residue sequence ALA520-PRO521-ALA522, associated with a turn structure in the RBD of the Up state protomer, acting as a stabilizing interaction with the NTD of its neighbor protomer. Additionally, our intra chain dominant energy mappings within each protomer, identified a significant “glue” point or possible “latch” for the Down state protomer between the S1 subdomain, SD1, and the RBD domain of the same protomer that was completely missing in the Up state protomer analysis. Ironically, this dominant energetic interaction in the Down state protomer involved the backbone atoms of the same three residue sequence ALA520-PRO521-ALA522 of the RBD with the amino acid R-group of GLN564 in the SD1 domain. Thus, this same three residue sequence acts as a stabilizer of the RBD in the Up conformation through its interactions with its neighboring NTD chain and a kind of latch in the Down state conformation through its interactions with its own SD1 domain. The dominant interaction energy residues identified here are also conserved across reported variations of SARS-CoV-2, as well as the closely related virions SARS-Cov and the bat corona virus RatG13. We conducted preliminary molecular dynamics simulations across 0.1 μ seconds to see if this latch provided structural stability and indeed found that a single point mutation (Q564G) resulted in the latch releasing transforming the protomer from the Down to the Up state conformation. Full trimeric Spike protein studies of the same mutation across all protomers, however, did not exhibit latch release demonstrating the critical importance of interchain interactions across the S1 domain, including RBD-NTD neighboring chain interactions. Therapies aimed at disrupting these noncovalent interactions could be a viable route for the physico-chemical mitigation of this deadly virion.
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Affiliation(s)
- Michael H. Peters
- Department of Chemical and Life Science Engineering, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail:
| | - Oscar Bastidas
- College of Biological Sciences, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Daniel S. Kokron
- NASA Ames Research Center, Moffett Field, California, United Sates of America
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4
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Rumpf CM, Longenbaugh RS, Henze CE, Chavez JC, Mathias DL. An Algorithmic Approach for Detecting Bolides with the Geostationary Lightning Mapper. Sensors (Basel) 2019; 19:s19051008. [PMID: 30818807 PMCID: PMC6427282 DOI: 10.3390/s19051008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 02/12/2019] [Accepted: 02/19/2019] [Indexed: 11/16/2022]
Abstract
The Geostationary Lightning Mapper (GLM) instrument onboard the GOES 16 and 17 satellites can be used to detect bolides in the atmosphere. This capacity is unique because GLM provides semi-global, continuous coverage and releases its measurements publicly. Here, six filters are developed that are aggregated into an automatic algorithm to extract bolide signatures from the GLM level 2 data product. The filters exploit unique bolide characteristics to distinguish bolide signatures from lightning and other noise. Typical lightning and bolide signatures are introduced and the filter functions are presented. The filter performance is assessed on 144845 GLM L2 files (equivalent to 34 days-worth of data) and the algorithm selected 2252 filtered files (corresponding to a pass rate of 1.44%) with bolide-similar signatures. The challenge of identifying frequent but small, decimeter-sized bolide signatures is discussed as GLM reaches its resolution limit for these meteors. The effectiveness of the algorithm is demonstrated by its ability to extract confirmed and new bolide discoveries. We provide discovery numbers for November 2018 when seven likely bolides were discovered of which four are confirmed by secondary observations. The Cuban meteor on Feb 1st 2019 serves as an additional example to demonstrate the algorithms capability and the first light curve as well as correct ground track was available within 8.5 hours based on GLM data for this event. The combination of the automatic bolide extraction algorithm with GLM can provide a wealth of new measurements of bolides in Earth's atmosphere to enhance the study of asteroids and meteors.
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Affiliation(s)
- Clemens M Rumpf
- NASA Advanced Supercomputing Division, NASA Ames Research Center, Moffett Field, CA 94035, USA.
- NASA Postdoctoral Program, USRA, Mountain View, CA 94043, USA.
| | - Randolph S Longenbaugh
- NASA Advanced Supercomputing Division, NASA Ames Research Center, Moffett Field, CA 94035, USA.
| | - Christopher E Henze
- NASA Advanced Supercomputing Division, NASA Ames Research Center, Moffett Field, CA 94035, USA.
| | | | - Donovan L Mathias
- NASA Advanced Supercomputing Division, NASA Ames Research Center, Moffett Field, CA 94035, USA.
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5
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Thompson SE, Coughlin JL, Hoffman K, Mullally F, Christiansen JL, Burke CJ, Bryson S, Batalha N, Haas MR, Catanzarite J, Rowe JF, Barentsen G, Caldwell DA, Clarke BD, Jenkins JM, Li J, Latham DW, Lissauer JJ, Mathur S, Morris RL, Seader SE, Smith JC, Klaus TC, Twicken JD, Van Cleve JE, Wohler B, Akeson R, Ciardi DR, Cochran WD, Henze CE, Howell SB, Huber D, Prša A, Ramírez SV, Morton TD, Barclay T, Campbell JR, Chaplin WJ, Charbonneau D, Christensen-Dalsgaard J, Dotson JL, Doyle L, Dunham EW, Dupree AK, Ford EB, Geary JC, Girouard FR, Isaacson H, Kjeldsen H, Quintana EV, Ragozzine D, Shporer A, Aguirre VS, Steffen JH, Still M, Tenenbaum P, Welsh WF, Wolfgang A, Zamudio KA, Koch DG, Borucki WJ. PLANETARY CANDIDATES OBSERVED BY Kepler. VIII. A FULLY AUTOMATED CATALOG WITH MEASURED COMPLETENESS AND RELIABILITY BASED ON DATA RELEASE 25. Astrophys J Suppl Ser 2018; 235:38. [PMID: 32908325 PMCID: PMC7477822 DOI: 10.3847/1538-4365/aab4f9] [Citation(s) in RCA: 255] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We present the Kepler Object of Interest (KOI) catalog of transiting exoplanets based on searching four years of Kepler time series photometry (Data Release 25, Q1-Q17). The catalog contains 8054 KOIs of which 4034 are planet candidates with periods between 0.25 and 632 days. Of these candidates, 219 are new in this catalog and include two new candidates in multi-planet systems (KOI-82.06 and KOI-2926.05), and ten new high-reliability, terrestrial-size, habitable zone candidates. This catalog was created using a tool called the Robovetter which automatically vets the DR25 Threshold Crossing Events (TCEs) found by the Kepler Pipeline (Twicken et al. 2016). Because of this automation, we were also able to vet simulated data sets and therefore measure how well the Robovetter separates those TCEs caused by noise from those caused by low signal-to-noise transits. Because of these measurements we fully expect that this catalog can be used to accurately calculate the frequency of planets out to Kepler's detection limit, which includes temperate, super-Earth size planets around GK dwarf stars in our Galaxy. This paper discusses the Robovetter and the metrics it uses to decide which TCEs are called planet candidates in the DR25 KOI catalog. We also discuss the simulated transits, simulated systematic noise, and simulated astrophysical false positives created in order to characterize the properties of the final catalog. For orbital periods less than 100 d the Robovetter completeness (the fraction of simulated transits that are determined to be planet candidates) across all observed stars is greater than 85%. For the same period range, the catalog reliability (the fraction of candidates that are not due to instrumental or stellar noise) is greater than 98%. However, for low signal-to-noise candidates found between 200 and 500 days, our measurements indicate that the Robovetter is 73.5% complete and 37.2% reliable across all searched stars (or 76.7% complete and 50.5% reliable when considering just the FGK dwarf stars). We describe how the measured completeness and reliability varies with period, signal-to-noise, number of transits, and stellar type. Also, we discuss a value called the disposition score which provides an easy way to select a more reliable, albeit less complete, sample of candidates. The entire KOI catalog, the transit fits using Markov chain Monte Carlo methods, and all of the simulated data used to characterize this catalog are available at the NASA Exoplanet Archive.
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Affiliation(s)
- Susan E. Thompson
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218
| | - Jeffrey L. Coughlin
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Kelsey Hoffman
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
| | - Fergal Mullally
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
- Orbital Insight, 100 W Evelyn Ave #110, Mountain View, CA 94041
| | | | - Christopher J. Burke
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
- MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-241, Cambridge, MA 02139
| | - Steve Bryson
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | | | | | - Joseph Catanzarite
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Jason F. Rowe
- Dept. of Physics and Astronomy, Bishop’s University, 2600 College St., Sherbrooke, QC, J1M 1Z7, Canada
| | - Geert Barentsen
- Bay Area Environmental Research Institute, 625 2nd St., Ste 209, Petaluma, CA 94952, USA
| | - Douglas A. Caldwell
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Bruce D. Clarke
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | | | - Jie Li
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
| | - David W. Latham
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA
| | | | - Savita Mathur
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - Robert L. Morris
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Shawn E. Seader
- Rincon Research Corporation,101 N Wilmot Rd, Tucson, AZ 85711
| | - Jeffrey C. Smith
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Todd C. Klaus
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Joseph D. Twicken
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | | | - Bill Wohler
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Rachel Akeson
- IPAC-NExScI, Mail Code 100-22, Caltech, 1200 E. California Blvd. Pasadena, CA 91125
| | - David R. Ciardi
- IPAC-NExScI, Mail Code 100-22, Caltech, 1200 E. California Blvd. Pasadena, CA 91125
| | - William D. Cochran
- McDonald Observatory and Department of Astronomy, University of Texas at Austin, Austin, TX 78712
| | | | | | - Daniel Huber
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- Institute for Astronomy, University of Hawai‘i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
- Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia
- Stellar Astrophysics Centre, Dept. of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Andrej Prša
- Villanova University, Dept. of Astrophysics and Planetary Science, 800 Lancaster Ave, Villanova PA 19085
| | - Solange V. Ramírez
- IPAC-NExScI, Mail Code 100-22, Caltech, 1200 E. California Blvd. Pasadena, CA 91125
| | - Timothy D. Morton
- Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
| | - Thomas Barclay
- NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771
| | - Jennifer R. Campbell
- NASA Ames Research Center, Moffett Field, CA 94035, USA
- KRBwyle, 2400 Nasa Parkway, Houston, TX 77058 USA
| | - William J. Chaplin
- Stellar Astrophysics Centre, Dept. of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
- School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - David Charbonneau
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA
| | - Jørgen Christensen-Dalsgaard
- Stellar Astrophysics Centre, Dept. of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | | | - Laurance Doyle
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- Institute for the Metaphysics of Physics, Principia College, One Maybeck Place, Elsah, Illinois 62028
| | | | - Andrea K. Dupree
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA
| | - Eric B. Ford
- Dept. of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA
- Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA
- Center for Astrostatistics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA
- Institute for CyberScience, The Pennsylvania State University
| | - John C. Geary
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA
| | - Forrest R. Girouard
- NASA Ames Research Center, Moffett Field, CA 94035, USA
- Orbital Sciences Corporation, 2401 East El Segundo Boulevard, Suite 200, El Segundo, CA 90245, USA
| | | | - Hans Kjeldsen
- Stellar Astrophysics Centre, Dept. of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Elisa V. Quintana
- NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771
| | - Darin Ragozzine
- Brigham Young University, Department of Physics and Astronomy, N283 ESC, Provo, UT 84602, USA
| | - Avi Shporer
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - Victor Silva Aguirre
- Stellar Astrophysics Centre, Dept. of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Jason H. Steffen
- University of Nevada, Las Vegas, 4505 S Maryland Pkwy, Las Vegas, NV 89154
| | - Martin Still
- Bay Area Environmental Research Institute, 625 2nd St., Ste 209, Petaluma, CA 94952, USA
| | - Peter Tenenbaum
- SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
- NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - William F. Welsh
- Department of Astronomy, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1221
| | - Angie Wolfgang
- Dept. of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA
- Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Khadeejah A Zamudio
- NASA Ames Research Center, Moffett Field, CA 94035, USA
- KRBwyle, 2400 Nasa Parkway, Houston, TX 77058 USA
| | - David G. Koch
- NASA Ames Research Center, Moffett Field, CA 94035, USA
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MacDougall PJ, Henze CE, Volkov A. Volume-rendering on a 3D hyperwall: A molecular visualization platform for research, education and outreach. J Mol Graph Model 2016; 70:1-6. [DOI: 10.1016/j.jmgm.2016.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 09/02/2016] [Accepted: 09/05/2016] [Indexed: 11/16/2022]
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Thompson SE, Mullally F, Coughlin J, Christiansen JL, Henze CE, Haas MR, Burke CJ. A MACHINE LEARNING TECHNIQUE TO IDENTIFY TRANSIT SHAPED SIGNALS. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/812/1/46] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Burke CJ, Christiansen JL, Mullally F, Seader S, Huber D, Rowe JF, Coughlin JL, Thompson SE, Catanzarite J, Clarke BD, Morton TD, Caldwell DA, Bryson ST, Haas MR, Batalha NM, Jenkins JM, Tenenbaum P, Twicken JD, Li J, Quintana E, Barclay T, Henze CE, Borucki WJ, Howell SB, Still M. TERRESTRIAL PLANET OCCURRENCE RATES FOR THEKEPLERGK DWARF SAMPLE. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/809/1/8] [Citation(s) in RCA: 272] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Jenkins JM, Twicken JD, Batalha NM, Caldwell DA, Cochran WD, Endl M, Latham DW, Esquerdo GA, Seader S, Bieryla A, Petigura E, Ciardi DR, Marcy GW, Isaacson H, Huber D, Rowe JF, Torres G, Bryson ST, Buchhave L, Ramirez I, Wolfgang A, Li J, Campbell JR, Tenenbaum P, Sanderfer D, Henze CE, Catanzarite JH, Gilliland RL, Borucki WJ. DISCOVERY AND VALIDATION OF Kepler-452b: A 1.6R⨁SUPER EARTH EXOPLANET IN THE HABITABLE ZONE OF A G2 STAR. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-6256/150/2/56] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Mullally F, Coughlin JL, Thompson SE, Rowe J, Burke C, Latham DW, Batalha NM, Bryson ST, Christiansen J, Henze CE, Ofir A, Quarles B, Shporer A, Eylen VV, Laerhoven CV, Shah Y, Wolfgang A, Chaplin WJ, Xie JW, Akeson R, Argabright V, Bachtell E, Barclay T, Borucki WJ, Caldwell DA, Campbell JR, Catanzarite JH, Cochran WD, Duren RM, Fleming SW, Fraquelli D, Girouard FR, Haas MR, Hełminiak KG, Howell SB, Huber D, Larson K, III TNG, Jenkins JM, Li J, Lissauer JJ, McArthur S, Miller C, Morris RL, Patil-Sabale A, Plavchan P, Putnam D, Quintana EV, Ramirez S, Aguirre VS, Seader S, Smith JC, Steffen JH, Stewart C, Stober J, Still M, Tenenbaum P, Troeltzsch J, Twicken JD, Zamudio KA. PLANETARY CANDIDATES OBSERVED BY
KEPLER
. VI. PLANET SAMPLE FROM Q1–Q16 (47 MONTHS). ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0067-0049/217/2/31] [Citation(s) in RCA: 216] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Seader S, Jenkins JM, Tenenbaum P, Twicken JD, Smith JC, Morris R, Catanzarite J, Clarke BD, Li J, Cote MT, Burke CJ, McCauliff S, Girouard FR, Campbell JR, Uddin AK, Zamudio KA, Sabale A, Henze CE, Thompson SE, Klaus TC. DETECTION OF POTENTIAL TRANSIT SIGNALS IN 17 QUARTERS OF
KEPLER
MISSION DATA. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0067-0049/217/1/18] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Rowe JF, Coughlin JL, Antoci V, Barclay T, Batalha NM, Borucki WJ, Burke CJ, Bryson ST, Caldwell DA, Campbell JR, Catanzarite JH, Christiansen JL, Cochran W, Gilliland RL, Girouard FR, Haas MR, Hełminiak KG, Henze CE, Hoffman KL, Howell SB, Huber D, Hunter RC, Jang-Condell H, Jenkins JM, Klaus TC, Latham DW, Li J, Lissauer JJ, McCauliff SD, Morris RL, Mullally F, Ofir A, Quarles B, Quintana E, Sabale A, Seader S, Shporer A, Smith JC, Steffen JH, Still M, Tenenbaum P, Thompson SE, Twicken JD, Laerhoven CV, Wolfgang A, Zamudio KA. PLANETARY CANDIDATES OBSERVED BY
KEPLER
. V. PLANET SAMPLE FROM Q1–Q12 (36 MONTHS). ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0067-0049/217/1/16] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Torres G, Kipping DM, Fressin F, Caldwell DA, Twicken JD, Ballard S, Batalha NM, Bryson ST, Ciardi DR, Henze CE, Howell SB, Isaacson HT, Jenkins JM, Muirhead PS, Newton ER, Petigura EA, Barclay T, Borucki WJ, Crepp JR, Everett ME, Horch EP, Howard AW, Kolbl R, Marcy GW, McCauliff S, Quintana EV. VALIDATION OF 12 SMALLKEPLERTRANSITING PLANETS IN THE HABITABLE ZONE. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/800/2/99] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Quintana EV, Barclay T, Raymond SN, Rowe JF, Bolmont E, Caldwell DA, Howell SB, Kane SR, Huber D, Crepp JR, Lissauer JJ, Ciardi DR, Coughlin JL, Everett ME, Henze CE, Horch E, Isaacson H, Ford EB, Adams FC, Still M, Hunter RC, Quarles B, Selsis F. An Earth-sized planet in the habitable zone of a cool star. Science 2014; 344:277-80. [PMID: 24744370 DOI: 10.1126/science.1249403] [Citation(s) in RCA: 227] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star's radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form.
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Affiliation(s)
- Elisa V Quintana
- SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043, USA
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Barclay T, Rowe JF, Lissauer JJ, Huber D, Fressin F, Howell SB, Bryson ST, Chaplin WJ, Désert JM, Lopez ED, Marcy GW, Mullally F, Ragozzine D, Torres G, Adams ER, Agol E, Barrado D, Basu S, Bedding TR, Buchhave LA, Charbonneau D, Christiansen JL, Christensen-Dalsgaard J, Ciardi D, Cochran WD, Dupree AK, Elsworth Y, Everett M, Fischer DA, Ford EB, Fortney JJ, Geary JC, Haas MR, Handberg R, Hekker S, Henze CE, Horch E, Howard AW, Hunter RC, Isaacson H, Jenkins JM, Karoff C, Kawaler SD, Kjeldsen H, Klaus TC, Latham DW, Li J, Lillo-Box J, Lund MN, Lundkvist M, Metcalfe TS, Miglio A, Morris RL, Quintana EV, Stello D, Smith JC, Still M, Thompson SE. A sub-Mercury-sized exoplanet. Nature 2013; 494:452-4. [DOI: 10.1038/nature11914] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/15/2013] [Indexed: 11/09/2022]
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Fressin F, Torres G, Rowe JF, Charbonneau D, Rogers LA, Ballard S, Batalha NM, Borucki WJ, Bryson ST, Buchhave LA, Ciardi DR, Désert JM, Dressing CD, Fabrycky DC, Ford EB, Gautier III TN, Henze CE, Holman MJ, Howard A, Howell SB, Jenkins JM, Koch DG, Latham DW, Lissauer JJ, Marcy GW, Quinn SN, Ragozzine D, Sasselov DD, Seager S, Barclay T, Mullally F, Seader SE, Still M, Twicken JD, Thompson SE, Uddin K. Two Earth-sized planets orbiting Kepler-20. Nature 2011; 482:195-8. [DOI: 10.1038/nature10780] [Citation(s) in RCA: 157] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 12/13/2011] [Indexed: 11/09/2022]
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Trent JD, Kagawa HK, Paavola CD, McMillan RA, Howard J, Jahnke L, Lavin C, Embaye T, Henze CE. Intracellular localization of a group II chaperonin indicates a membrane-related function. Proc Natl Acad Sci U S A 2003; 100:15589-94. [PMID: 14673104 PMCID: PMC307612 DOI: 10.1073/pnas.2136795100] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2003] [Indexed: 11/18/2022] Open
Abstract
Chaperonins are protein complexes that are believed to function as part of a protein folding system in the cytoplasm of the cell. We observed, however, that the group II chaperonins known as rosettasomes in the hyperthermophilic archaeon Sulfolobus shibatae, are not cytoplasmic but membrane associated. This association was observed in cultures grown at 60 degrees C and 76 degrees C or heat-shocked at 85 degrees C by using immunofluorescence microscopy and in thick sections of rapidly frozen cells grown at 76 degrees C by using immunogold electron microscopy. We observed that increased abundance of rosettasomes after heat shock correlated with decreased membrane permeability at lethal temperature (92 degrees C). This change in permeability was not seen in cells heat-shocked in the presence of the amino acid analogue azetidine 2-carboxylic acid, indicating functional protein synthesis influences permeability. Azetidine experiments also indicated that observed heat-induced changes in lipid composition in S. shibatae could not account for changes in membrane permeability. Rosettasomes purified from cultures grown at 60 degrees C and 76 degrees C or heat-shocked at 85 degrees C bind to liposomes made from either the bipolar tetraether lipids of Sulfolobus or a variety of artificial lipid mixtures. The presence of rosettasomes did not significantly change the transition temperature of liposomes, as indicated by differential scanning calorimetry, or the proton permeability of liposomes, as indicated by pyranine fluorescence. We propose that these group II chaperonins function as a structural element in the natural membrane based on their intracellular location, the correlation between their functional abundance and membrane permeability, and their potential distribution on the membrane surface.
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Affiliation(s)
- Jonathan D Trent
- National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA 94035, USA.
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