Effects of bicarbonate and formate on the donor side of Photosystem 2
Effects of bicarbonate and formate on the donor side of Photosystem 2
复制标题
碳酸氢盐和甲酸盐对光系统 2 供体侧的影响
DOI：
10.1007/bf00020434
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发表时间：
1995
影响因子：
3.7
通讯作者：
Y. Feyziev
中科院分区：
文献类型：
--
作者：
V. V. Klimov;S. Allakhverdiev;S. Baranov;Y. Feyziev
浓度为5~20μM的甲酸钠抑制豌豆亚叶绿体膜(DT-20)中光系统2(PS 2)供体侧的电子流动，表现为抑制光诱导的与初级和中间电子受体QA和叶绿素的光还原相关的叶绿素荧光产量的变化和放氧作用，以及与初级电子供体P680的光氧化相关的吸光度变化的增加。当介质中重碳酸盐部分耗尽时，这些活性也被抑制，并通过添加0.1-10 mM的NaHCO3来恢复。当M甲酸盐的浓度高于20μ时，在PS 2的受体侧诱导已知的碳酸氢盐效应，该效应在毫摩尔浓度下占主导地位。在经Tris处理(缺锰)的DT-20分子筛中，只有在加入5μNaHCO3后，才能有效地用0.2mMMnCl2(每个PS2反应中心4个锰原子)在无重碳酸盐介质中恢复电子流。在NaHCO3存在下的修复伴随着Mn2+与PS 2膜功能结合的增加，这一点从沉淀法或加入EDTA去除添加的Mn2+的实验中得到了证实。预光照增加了重碳酸盐存在时的锰结合。数据表明，PS-2给体一侧的碳酸氢盐效应与相对低亲和力的碳酸氢盐结合池有关。结果表明，碳酸氢钠作为一种必需配体或通过修饰锰的结合部位(S)参与了水氧化锰团簇的形成。
Sodium formate at concentration of 5–20 μM suppresses electron flow on the donor side of Photosystem 2 (PS 2) in pea subchloroplast membranes (DT-20) which is revealed by inhibition of photoinduced changes of chlorophyll fluorescence yield related to photoreduction of QAand pheophytin (the primary and intermediary electron acceptors) and oxygen evolution and the increase of absorbance changes related to photooxidation of P680, the primary electron donor, under continuous illumination. These activities are also inhibited upon partial depletion of bicarbonate in the medium and restored by the addition of 0.1–10 mM NaHCO3. At concentrations higher than 20 μM formate induces the known bicarbonate effect on the acceptor side of PS 2 which dominates at millimolar concentrations of the agent. In Tris-treated (Mn-depleted) DT-20 the restoration of electron flow with 0.2 μM MnCl2(4 Mn atoms per one PS 2 reaction center) in the medium depleted of bicarbonate is efficient only after the addition of 5 mM NaHCO3. The restoration in the presence of NaHCO3is accompanied by an increased functional binding of Mn2+to PS 2 membranes which is confirmed by experiments on removal of added Mn2+by either sedimentation or the addition of EDTA. Pre-illumination increases the Mn binding in the presence of bicarbonate. The data show that the bicarbonate effect on the donor side of PS 2 is related to a relatively low-affinity bound pool of bicarbonate. It is suggested that bicarbonate takes part in the formation of the Mn-cluster capable of water oxidation as an obligatory ligand or through modification of the binding site(s) of Mn.