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Structural and spectropotentiometric analysis of Blastochloris viridis heterodimer mutant reaction center

Ponomarenko, Nina S. and Li, Liang and Marino, Antony R. and Tereshko, Valentina and Ostafin, Agnes and Popova, Julia A. and Bylina, Edward J. and Ismagilov, Rustem F. and Norris, JrJames R., Jr. (2009) Structural and spectropotentiometric analysis of Blastochloris viridis heterodimer mutant reaction center. Biochimica et Biophysica Acta - Biomembranes, 1788 . pp. 1822-1831. ISSN 0005-2736.

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Heterodimer mutant reaction centers (RCs) of Blastochloris viridis were crystallized using microfluidic technology. In this mutant, a leucine residue replaced the histidine residue which had acted as a fifth ligand to the bacteriochlorophyll (BChl) of the primary electron donor dimer M site (HisM200). With the loss of the histidine-coordinated Mg, one bacteriochlorophyll of the special pair was converted into a bacteriopheophytin (BPhe), and the primary donor became a heterodimer supermolecule. The crystals had dimensions 400 × 100 ×100 μm, belonged to space group P43212, and were isomorphous to the ones reported earlier for the wild type (WT) strain. The structure was solved to a 2.5 Å resolution limit. Electron-density maps confirmed the replacement of the histidine residue and the absence of Mg. Structural changes in the heterodimer mutant RC relative to the WT included the absence of the water molecule that is typically positioned between the M side of the primary donor and the accessory BChl, a slight shift in the position of amino acids surrounding the site of the mutation, and the rotation of the M194 phenylalanine. The cytochrome subunit was anchored similarly as in the WT and had no detectable changes in its overall position. The highly conserved tyrosine L162, located between the primary donor and the highest potential heme C380, revealed only a minor deviation of its hydroxyl group. Concomitantly to modification of the BChl molecule, the redox potential of the heterodimer primary donor increased relative to that of the WT organism (772 mV vs. 517 mV). The availability of this heterodimer mutant and its crystal structure provides opportunities for investigating changes in light-induced electron transfer that reflect differences in redox cascades.

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Ismagilov, Rustem F.0000-0002-3680-4399
Additional Information:© 2009 Elsevier. Open Access article. Received 30 January 2009. Revised 6 May 2009. Accepted 3 June 2009. Available online 17 June 2009. We gratefully acknowledge support from the US Department of Energy, Office of Basic Energy Sciences, and Division of Chemical Sciences Contract DEFG02-96ER14675. This work was supported in part through the NIH Roadmap for Medical Research (R01 GM075827-01). We thank Elizabeth B. Haney for contributions to editing this manuscript. L.L and R.F.I. are responsible for the microfluidic crystallization.
Funding AgencyGrant Number
Department of Energy (DOE)DEFG02-96ER14675
NIHR01 GM075827-01
Subject Keywords:Blastochloris viridis; Heterodimer mutant; Reaction center structure; Primary donor redox potential; Photosynthetic reaction center; Microfluidic
Record Number:CaltechAUTHORS:20130821-160729461
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40857
Deposited By: Whitney Barlow
Deposited On:26 Aug 2013 23:57
Last Modified:03 Oct 2019 05:43

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