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首页> 外文期刊>Biochemistry >Thermodynamics of Charge Separation of Photosystem I in the menA and menB Null Mutants of Synechocystis sp. PCC 6803 Determined by Pulsed Photoacoustics
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Thermodynamics of Charge Separation of Photosystem I in the menA and menB Null Mutants of Synechocystis sp. PCC 6803 Determined by Pulsed Photoacoustics

机译：拟南芥sp。menA和menB Null突变体中光系统I电荷分离的热力学。 PCC 6803由脉冲光声确定

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When the biosynthesis of phylloquinone is inhibited in Synechocystis sp. PCC 6803 byninterrupting the menA or the menB gene, photosystem I (PS I) recruits plastoquinone-9 (AP) to occupy thenA1 sites. In PS I from the menA and menB null mutants, forward electron transfer from the quinone to thenFeS clusters occurs approximately 1000 times slower than in wild-type PS I [Semenov, A. Yu., Vassiliev,nI. R., van der Est, A., Mamedov, M. D., Zybailov, B., Shen, G., Stehlik, D., Diner, B. A., Chitnis, P. R.,nand Golbeck, J. H. (2000) J. Biol. Chem. 275, 23429-23438]. To investigate the effect on thermodynamics,nthe enthalpy and volume changes of charge separation in PS I in the menA and menB mutants werenmeasured using pulsed time-resolved photoacoustics on the nanosecond and microsecond time scales.nThe observed thermodynamic data are the same for the menA and menB mutants. This is expected becausenthe recruited quinone (AP) is the same in both mutants. The volume change of PS I from the mutantsnfollowing charge separation on both time scales was -17 ( 2 Å3, less than that of the wild type, -21 Å3.nThe quantum yield of charge separation was found to be slightly lower (85 ( 9%) than that of wild-typenPS I (96 ( 10%). The observed reaction is assigned to the formation of P700n+APn- from P700*AP. Annenthalpy change (ΔH) of -0.69 ( 0.07 eV was obtained for this reaction. In contrast, a larger enthalpynchange -0.8 eV for the formation of P700n+A1n- from P700* and an apparent entropy change (TΔS, T ) 25n°C) of -0.2 eV were obtained in wild-type PS I [Hou, H. J. M., and Mauzerall, D. (2006) J. Am. Chem.nSoc. 128, 1580-1586]. Taking the free energy to be -0.70 eV in PS I of the mutants, the apparentnentropy is close to zero in the mutants. Since the apparent entropy change for the overall reaction of thenproduction of P700n+FA/Bn- from P700* is very likely the same as that of the wild type, +0.35 eV, thisnimplies that the reaction of P700n+APn-FA/B f P700n+APFA/Bn- in the mutants is almost completely entropyndriven (ΔG ) -0.07 eV and TΔS ) +0.40 eV). These results show that not only the kinetics but alsonthe thermodynamics of electron transfer reactions in PS I are significantly affected by the recruitment ofnthe foreign plastoquinone-9 into the A1 site.
机译：当叶绿体菌种中的叶绿醌的生物合成受到抑制时。 PCC 6803通过中断menA或menB基因，光系统I（PS I）募集了质体醌9（AP）占据了当时的A1位点。在来自menA和menB无效突变体的PS I中，从醌到FeS簇的正向电子转移比野生型PS I慢约1000倍[Semenov，A. Yu。，Vassiliev，nI。 R.，van der Est，A.，Mamedov，M. D.，Zybailov，B.，Shen，G.，Stehlik，D.，Diner，B.A.，Chitnis，P.R.，nand Golbeck，J.H.（2000）J.Biol。化学275，23429-23438]。为了研究对热力学的影响，使用脉冲时间分辨光声技术在纳秒和微秒时间尺度上测量了menA和menB突变体中PS I的电荷分离的焓和体积变化.n观察到的menA和menB突变体。这是可以预期的，因为两个突变体中募集的醌（AP）相同。在两个时间尺度上，随着电荷分离，突变体中PS I的体积变化为-17（2Å3，小于野生型-21Å3.n）发现电荷分离的量子产率稍低（85（9 ％）比野生型nPS I（96（10％）。观察到的反应归因于由P700 * AP形成P700n + APn-。负焓变化（ΔH）为-0.69（该反应获得0.07 eV相反，在野生型PS I中，从P700 *形成P700n + A1n-的焓变较大-0.8 eV，表观熵变（TΔS，T）25n°C）为-0.2 eV [Hou， HJM和Mauzerall，D.（2006）J. Am。Chem.nSoc。128，1580-1586]。以突变体PS I中的自由能为-0.70 eV，表观熵在突变体中接近于零由于从P700 *产生P700n + FA / Bn-的整个反应的表观熵变化很可能与野生型的+0.35 eV相同，这意味着P700n + AP的反应突变体中的n-FA / B f P700n + APFA / Bn-几乎完全被熵驱动（ΔG）-0.07 eV和TΔS）+0.40 eV）。这些结果表明，PS I中不仅电子转移反应的动力学而且热动力学都受到外来质体醌9募集到A1位点的显着影响。

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  • 来源
    《Biochemistry》 |2009年第8期|p.1829-1837|共9页
  • 作者

    Harvey J. M. Hou Gaozhong Shen Vladimir A. Boichenko John H. Golbeck and David Mauzerall;

  • 作者单位

    Department of Chemistry and Biochemistry, UniVersity of Massachusetts Dartmouth, North Dartmouth,Massachusetts 02747, Department of Biochemistry and Molecular Biology and Department of Chemistry, The PennsylVaniaState UniVersity, UniVersity Park, PennsylVania 16802, Institute of Basic Biological Problems, Russian Academy of Sciences,Pushchino 142290, Russia, and The Rockefeller UniVersity, 1230 York AVenue, New York, New York 10065;

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