Shinkarev V P
Department of Plant Biology, University of Illinois, Urbana 61801-3838, USA.
Photochem Photobiol. 1998 Jun;67(6):683-99. doi: 10.1562/0031-8655(1998)067<0683:tgkmoe>2.3.co;2.
A new general kinetic model for the functioning of photosynthetic reaction centers (RC) of purple bacteria, under multiple flash activation, has been developed. The model includes the primary electron donor (P870) as well as the primary (QA) and secondary (QB) acceptor quinones. The new features of this general model include: (1) consideration of four different states of the QB binding site (vacant, occupied by QB, by QB- and by QBH2), (2) incorporation of the dark relaxation of the RC between flashes, (3) the assumption of fast exchange of quinones between the RC and quinone pool in detergent micelles or chromatophore membrane, (4) description of the kinetics of electron transfer in both oxidized (no donor for P870+) and reduced (in the presence of donor for P870+) conditions simultaneously, (5) the consideration of both single and multiple flash activation of the RC of purple bacteria and (6) consideration of the cumulative effects of all previous flashes of the series in the response induced by the current flash. This model is used to calculate and predict (1) flash-induced binary oscillations of the secondary acceptor semiquinone (QB-), (2) flash-induced behavior of P870+ in the presence and absence of electron donor and (3) the apparent equilibrium constant of electron transfer between QA and QB and others. Different characteristics of RC are analyzed as a function of flash intensity, time between flashes, concentration of electron donor, redox-potential of the medium, concentration of pool quinone and quinol, association and dissociation equilibrium constants for quinone and quinol at the QB binding site, equilibrium constants of electron transfer between QA- and QB and between QA- and QB-, as well as the rate constants of oxidation of QA- and QB- by redox mediators. The proposed model can be used as a basis for assays of kinetic behavior of native and mutant RC of purple bacteria and for determination of the factors influencing the release of QH2 from RC. The latter is needed for analysis of factors controlling light-activated electron transport in the cytochrome bc1 complexes of purple bacteria by quinol molecules released from RC. The developed general approach for parallel consideration of flash-induced transitions of RC and its following dark relaxation between flashes can also be used for kinetic description of photosynthetic RC of oxygenic photosynthesis.
已经建立了一个新的通用动力学模型，用于描述紫色细菌光合反应中心（RC）在多次闪光激活下的功能。该模型包括初级电子供体（P870）以及初级受体醌（QA）和次级受体醌（QB）。这个通用模型的新特点包括：（1）考虑QB结合位点的四种不同状态（空的、被QB占据、被QB-占据和被QBH2占据）；（2）纳入闪光之间RC的暗弛豫；（3）假设在去污剂胶束或色素体膜中，醌在RC和醌池之间快速交换；（4）同时描述氧化状态（P870+无供体）和还原状态（P870+有供体）下的电子转移动力学；（5）考虑紫色细菌RC的单次和多次闪光激活；（6）考虑该系列中所有先前闪光在当前闪光诱导的响应中的累积效应。该模型用于计算和预测：（1）闪光诱导的次级受体半醌（QB-）的二元振荡；（2）在有和没有电子供体的情况下P870+的闪光诱导行为；（3）QA和QB之间电子转移的表观平衡常数等。作为闪光强度、闪光间隔时间、电子供体浓度、介质氧化还原电位、醌池醌和氢醌浓度、醌和氢醌在QB结合位点的缔合和解离平衡常数、QA-和QB之间以及QA-和QB-之间电子转移的平衡常数以及QA-和QB-被氧化还原介质氧化的速率常数的函数，分析了RC的不同特性。所提出的模型可作为分析紫色细菌天然和突变RC动力学行为以及确定影响QH2从RC释放的因素的基础。后者对于分析通过从RC释放的氢醌分子控制紫色细菌细胞色素bc1复合物中光激活电子传递的因素是必要的。所开发的用于并行考虑RC的闪光诱导转变及其随后闪光之间的暗弛豫的通用方法，也可用于对光合放氧光合作用的光合RC进行动力学描述。
