Biochemical characterization of RecA variants that contribute to extreme resistance to ionizing radiation |
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| Affiliation: | 1. Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706-1544, United States;2. Department of Chemistry, National Taiwan University, Taipei, Taiwan;3. Department of Biomolecular Chemistry, University of Wisconsin–Madison, Madison, WI 53706, United States;4. Department of Biological Sciences, Louisiana State University and A & M College, Baton Rouge, LA 70803, United States;1. Uppsala University;2. Karolinska Institutet;1. Department of Biophysics, GSI Helmholtz Center for Heavy Ion Research, Planckstrasse 1, 64291 Darmstadt, Germany;2. Institute for Condensed Matter Physics, Darmstadt University of Technology, 64289 Darmstadt, Germany;1. Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan;2. Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan;3. Radioisotope Research Center, Teikyo University, Kaga Itabashi-ku, Tokyo 173-8605, Japan;4. Department of Ophthalmology, Hiroshima Memorial Hospital, Honkawacho, Naka-ku, Hiroshima 730-0802, Japan;1. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia;2. National University of Science and Technology (MISiS), Leninsky Prospekt, 4, Moscow 119049 Russia;3. Fomos-Materials, Buzheninova 16, Moscow 107023, Russia;4. Institute of Physics AS CR, Cukrovarnicka 10, 162 00 Prague, Czech Republic;5. Institute of Light and Matter, CNRS, University Lyon 1, Villeurbanne 69622, France;6. Plateforme Cristalinnov Site de Montmélian, Cleanspace-354 Voie Magellan Parc d׳activité Alpespace, F-73800 Sainte-Hélène du Lac, France;7. Institute of Physics, University of Tartu, W. Ostwaldi Str.1, 50411 Tartu, Estonia |
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| Abstract: | Among strains of Escherichia coli that have evolved to survive extreme exposure to ionizing radiation, mutations in the recA gene are prominent and contribute substantially to the acquired phenotype. Changes at amino acid residue 276, D276A and D276N, occur repeatedly and in separate evolved populations. RecA D276A and RecA D276N exhibit unique adaptations to an environment that can require the repair of hundreds of double strand breaks. These two RecA protein variants (a) exhibit a faster rate of filament nucleation on DNA, as well as a slower extension under at least some conditions, leading potentially to a distribution of the protein among a higher number of shorter filaments, (b) promote DNA strand exchange more efficiently in the context of a shorter filament, and (c) are markedly less inhibited by ADP. These adaptations potentially allow RecA protein to address larger numbers of double strand DNA breaks in an environment where ADP concentrations are higher due to a compromised cellular metabolism. |
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| Keywords: | RecA protein Radiation resistance Evolution Double strand break repair DNA repair |
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