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首页> 外文期刊>Biochemistry >EFFECTS OF HYDROGEN BENDING TO A BACTERIOCHLOROPHYLL-BACTERIOPHEOPHYTIN DIMER IN REACTION CENTERS FROM RHODOBACTER SPHAEROIDES
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EFFECTS OF HYDROGEN BENDING TO A BACTERIOCHLOROPHYLL-BACTERIOPHEOPHYTIN DIMER IN REACTION CENTERS FROM RHODOBACTER SPHAEROIDES

机译：球状藻类细菌反应中心中细菌与细菌-叶绿素-细菌-植物生长素二聚体的氢键作用

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The properties of the primary electron donor in reaction centers from Rhodobacter sphaeroides have been investigated in mutants containing a bacteriochlorophyll (BChl)-bacteriopheophytin (BPhe) dimer with and without hydrogen bonds to the conjugated carbonyl groups. The heterodimer mutation His M202 to Leu was combined with each of the following mutations: His L168 to Phe, which should remove an existing hydrogen bond to the BChl molecule; Leu L131 to His, which should add a hydrogen bond to the BChl molecule; and Leu M160 to His and Phe M197 to His, each of which should add a hydrogen bond to the BPhe molecule [Rautter, J., Lendzian, F., Schulz, C,, Fetsch, A,, Kuhn, M,, Lin, X., Williams, J. C,, Allen, J. P., & Lubitz, W. (1995) Biochemistry 34, 8130-8143]. Pigment extractions and Fourier transform Raman spectra confirm that all of the mutants contain a heterodimer. The bands in the resonance Raman spectra arising from the BPhe molecule, which is selectively enhanced, exhibit the shifts expected for the addition of a hydrogen bond to the 9-keto and 2-acetyl carbonyl groups. The oxidation-reduction midpoint potential of the donor is increased by approximately 85 mV by the addition of a hydrogen bond to the BChl molecule but is only increased by approximately 15 mV by the addition of a hydrogen bond to the BPhe molecule. An increase in the rate of charge recombination from the primary quinone is correlated with an increase in the midpoint potential. The yield of electron transfer to the primary quinone is 5-fold reduced for the mutants with a hydrogen bond to the BPhe molecule. Room- and low-temperature optical absorption spectra show small differences from the features that are typical for the heterodimer, except that a large increase in absorption is observed around 860-900 nm for the donor a. band in the mutant that adds a hydrogen bond to the BChl molecule. The changes in the optical spectra and the yield of electron transfer are consistent with a model in which the addition of a hydrogen bond to the BChl molecule increases the energy of an internal charge transfer state while the addition to the BPhe molecule stabilizes this state. The results show that the properties of the heterodimer are different depending on which side is hydrogen-bonded and suggest that the hydrogen bonds alter the energy of the internal charge transfer state in a well-defined manner.
机译：在包含细菌叶绿素（BChl）-细菌脱镁叶绿素（BPhe）二聚体的突变体中，研究了球形球形红球菌在反应中心的一次电子供体的性质。 His M202突变为Leu的异二聚体突变与以下每种突变结合：His L168突变为Phe，这应去除BChl分子的现有氢键; Leu L131到His上，这应该在BChl分子上加氢键; Leu M160到His以及Phe M197到His，每个都应在BPhe分子上添加氢键[Rautter，J.，Lendzian，F.，Schulz，C ,, Fetsch，A ,, Kuhn，M，Lin ，X.，Williams，J.C.，Allen，JP，＆Lubitz，W。（1995）Biochemistry 34，8130-8143]。颜料提取和傅里叶变换拉曼光谱证实所有突变体均含有异二聚体。由BPhe分子产生的共振拉曼光谱中的能带被选择性增强，表现出预期向9-酮和2-乙酰基羰基加氢键的位移。供体的氧化还原中点电势通过在BChl分子上添加氢键而增加了约85 mV，但通过在BPhe分子上添加氢键而仅增加了约15 mV。来自伯醌的电荷复合速率的增加与中点电位的增加相关。对于与BPhe分子具有氢键的突变体，电子转移至伯醌的产率降低了5倍。室温和低温光吸收光谱显示出与异二聚体的典型特征的细微差异，不同之处在于供体a在860-900 nm附近观察到吸收的大幅增加。突变体中的带，其向BChl分子添加氢键。光谱的变化和电子转移的产率与模型相符，在该模型中，向BChl分子添加氢键会增加内部电荷转移状态的能量，而向BPhe分子添加则会稳定该状态。结果表明，异二聚体的性质取决于哪一侧是氢键结合的，并且表明氢键以明确的方式改变了内部电荷转移态的能量。

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