Crofts A R, Yerkes C T
Program in Biophysics and Computational Biology, University of Illinois, Urbana 61801.
FEBS Lett. 1994 Oct 3;352(3):265-70. doi: 10.1016/0014-5793(94)00976-7.
We discuss energy-dependent fluorescence lowering (qE-quenching), and suggest a model to explain the experimental data currently available. The main elements of the model are: (a) the qE-quenching reflects a mechanism associated with a component of the light-harvesting antenna rather than the reaction center of photosystem (PS) II--we suggest that it occurs through formation of an efficient quencher in one of the minor chlorophyll protein (CP) complexes; (b) the minor CPs have glutamate residues instead of glutamines at positions shown in light-harvesting complex II (LHCII) to be ligands to chlorophylls near the lumenal interface. We suggest that the quenching reflects a change in ligation of chlorophyll on protonation of these glutamate residues leading to formation of an exciton coupled dimer with a neighboring pigment, in which additional energy levels allow vibrational relaxation of the excited singlet. The model accounts for the dependence on low lumenal pH, the ligand residue changes between LHCII and the minor CPs, the preferential distribution of components of the xanthophyll cycle in the minor CPs, the inhibition of qE-quenching by DCCD, and the specific binding of DCCD to the minor CPs.
我们讨论了能量依赖型荧光淬灭（qE 淬灭），并提出了一个模型来解释目前可用的实验数据。该模型的主要要素包括：（a）qE 淬灭反映了一种与捕光天线的一个组分相关的机制，而非光系统（PS）II 的反应中心——我们认为它是通过在一种次要的叶绿素蛋白（CP）复合物中形成一种高效淬灭剂而发生的；（b）次要的 CP 在捕光复合物 II（LHCII）中显示为与类囊体腔界面附近叶绿素配体的位置上具有谷氨酸残基而非谷氨酰胺残基。我们认为，淬灭反映了这些谷氨酸残基质子化时叶绿素配体的变化，导致与相邻色素形成激子耦合二聚体，其中额外的能级允许激发单重态的振动弛豫。该模型解释了对低类囊体腔 pH 的依赖性、LHCII 和次要 CP 之间的配体残基变化、叶黄素循环组分在次要 CP 中的优先分布、DCCD 对 qE 淬灭的抑制作用以及 DCCD 与次要 CP 的特异性结合。
