An isotope-edited FTIR investigation of the role of Ser-L223 in binding quinone (QB) and semiquinone (QB-) in the reaction center from Rhodobacter sphaeroides.
An isotope-edited FTIR investigation of the role of Ser-L223 in binding quinone (QB) and semiquinone (QB-) in the reaction center from Rhodobacter sphaeroides.
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通过同位素编辑 FTIR 研究 Ser-L223 在球形红杆菌反应中心结合醌 (QB) 和半醌 (QB-) 中的作用。
DOI：
10.1021/bi051328d
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Breton,Jacques
中科院分区：
文献类型：
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作者：
Nabedryk,Eliane;Paddock,MarkL;Okamura,MelvinY;Breton,Jacques
在紫色细菌Rhodobacter sphaeroides的光合反应中心（RC）中，质子耦合的电子转移反应发生在次级醌（QB）位点。附近的几个残基是重要的结合和氧化还原化学参与的光诱导转换从QB到醌QBH 2。Ser-L223是位于QB附近的重要功能残基之一。为了获得关于Ser-L223和QB-之间的相互作用的信息，在其中Ser-L223被Ala替换的突变RC中测量同位素编辑的QB-/QB FTIR差谱，并与天然RC进行比较。同位素编辑的CO红外指纹谱 和CC 突变体中的QB（QB-）模式基本上与天然RC的QB模式相同。这些发现表明，在天然和突变体RC中，QB和QB-与蛋白质的相互作用是高度等效的。这些结果的最简单的解释是Ser-L223不与QB或QB-形成氢键，但可能与附近的酸基形成氢键，优选Asp-L213。Ser OH质子从Asp-L213到QB-的旋转被认为是质子转移到还原醌的重要步骤。此外，还原的醌保持牢固的结合，表明其他不同的氢键对稳定QB-更重要。QB结合位点的设计特征的影响进行了讨论。
In the photosynthetic reaction center (RC) from the purple bacteriumRhodobacter sphaeroides, proton-coupled electron-transfer reactions occur at the secondary quinone (QB) site. Several nearby residues are important for both binding and redox chemistry involved in the light-induced conversion from QBto quinol QBH2. Ser-L223 is one of the functionally important residues located near QB. To obtain information on the interaction between Ser-L223 and QBand QB-, isotope-edited QB-/QBFTIR difference spectra were measured in a mutant RC in which Ser-L223 is replaced with Ala and compared to the native RC. The isotope-edited IR fingerprint spectra for the CO and CC modes of QB(QB-) in the mutant are essentially the same as those of the native RC. These findings indicate that highly equivalent interactions of QBand QB-with the protein occur in both native and mutant RCs. The simplest explanation of these results is that Ser-L223 is not hydrogen bonded to QBor QB-but presumably forms a hydrogen bond to a nearby acid group, preferentially Asp-L213. The rotation of the Ser OH proton from Asp-L213 to QB-is expected to be an important step in the proton transfer to the reduced quinone. In addition, the reduced quinone remains firmly bound, indicating that otherdistincthydrogen bonds are more important for stabilizing QB-. Implications on the design features of the QBbinding site are discussed.