Engineering of an alternative electron transfer path in photosystem II
Engineering of an alternative electron transfer path in photosystem II
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DOI：
10.1073/pnas.1000187107
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发表时间：
2010-05-25
影响因子：
11.1
通讯作者：
Adir, Noam
中科院分区：
文献类型：
--
作者：
Larom, Shirley;Salama, Faris;Adir, Noam
氧光合作用电子转移的初始步骤发生在光系统II中，这是一个复杂的色素/蛋白质跨膜复合体。光驱动的电子转移发生在一个多步骤的途径，有效地隔绝竞争的电子转移途径。电子传递系统的核心，由六个线性耦合的氧化还原活性辅助因子组成，使电子从水转移到二级醌受体Q(B)，主要嵌入两种称为D1和D2的蛋白质中。我们已经在硅中确定了一个位点，它位于Q(a)中间醌受体附近，可以作为氧化还原活性蛋白的潜在结合位点。本研究表明，在藻胞杆菌PCC 6803中，将D1蛋白的赖氨酸238修饰为谷氨酸（Glu），导致菌株光自养生长。Glu类囊体膜能够以水作为电子供体进行外源细胞色素c的光依赖性还原。当分离的类囊体膜被照射时，Glu突变体的细胞色素c光还原也显示出显著的保护D1蛋白免受光损伤。因此，我们设计了一种新的电子从水转移到可溶性蛋白质电子载体的途径，而不会损害光系统II的正常功能。
The initial steps of oxygenic photosynthetic electron transfer occur within photosystem II, an intricate pigment/protein transmembrane complex. Light-driven electron transfer occurs within a multi-step pathway that is efficiently insulated from competing electron transfer pathways. The heart of the electron transfer system, composed of six linearly coupled redox active cofactors that enable electron transfer from water to the secondary quinone acceptor Q(B), is mainly embedded within two proteins called D1 and D2. We have identified a site in silico, poised in the vicinity of the Q(A) intermediate quinone acceptor, which could serve as a potential binding site for redox active proteins. Here we show that modification of Lysine 238 of the D1 protein to glutamic acid (Glu) in the cyanobacterium Synechocystis sp. PCC 6803, results in a strain that grows photautotrophically. The Glu thylakoid membranes are able to perform light-dependent reduction of exogenous cytochrome c with water as the electron donor. Cytochrome c photoreduction by the Glu mutant was also shown to significantly protect the D1 protein from photodamage when isolated thylakoid membranes were illuminated. We have therefore engineered a novel electron transfer pathway from water to a soluble protein electron carrier without harming the normal function of photosystem II.