Phosphatidylglycerol requirement for the function of electron acceptor plastoquinone QB in the photosystem II reaction center
Phosphatidylglycerol requirement for the function of electron acceptor plastoquinone QB in the photosystem II reaction center
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DOI：
10.1021/bi011884h
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发表时间：
2002-03-19
期刊：
影响因子：
2.9
通讯作者：
Wada, H
中科院分区：
文献类型：
--
作者：
Gombos, Z;Várkonyi, Z;Wada, H
磷脂酰甘油（PG）是叶绿体和蓝藻类囊体膜中普遍存在的一种成分，被证明在氧合光合作用的光系统II反应中心对质体醌电子受体Q(B)的功能至关重要。据报道，Synechocystis' sp. PCC6803的pgsA突变体细胞在不含PG的培养基中生长，导致PG含量降低90%，光合进化氧活性降低50% [Hagio， M., Gombos， Z., Varkonyi， Z., Masamoto， K., Sato， N., Tsuzuki， M., and Wada， H. (2000) Plant Physiol. 124, 795-804]。我们研究了pgsA突变体光系统II中电子传递的每一步，以明确PG的功能位点。在连续和闪光照射下，叶绿素荧光产量的快速上升表明Q(A)（-）的积累。Q(A)（-）被Q(B)质体醌氧化变得缓慢，而Q(A)（-）再氧化需要几秒钟，当双闪光荧光测量时。热释光测量进一步表明，PG剥夺后S(2)Q(A)（-）态积累，但S(2)Q(B)（-）态没有积累。这些结果表明，PG剥夺使Q(B)质体醌功能失活。我们认为PG是维持Q(B)结合位点结构完整性的光系统II反应中心复合物不可或缺的组成部分。这些发现首次明确了PG在光合反应中心的特定功能位点。
Phosphatidylglycerol (PG), a ubiquitous constituent of thylakoid membranes of chloroplasts and cyanobacteria, is demonstrated to be essential for the functionality of plastoquinone electron acceptor Q(B) in the photosystem II reaction center of oxygenic photosynthesis. Growth of the pgsA mutant cells of Synechocystis' sp. PCC6803 that are defective in phosphatidylglycerolphosphate synthase and are incapable of synthesizing PG, in a medium without PG, resulted in a 90% decrease in PG content and a 50% loss of photosynthetic oxygen-evolving activity as reported [Hagio, M., Gombos, Z., Varkonyi, Z., Masamoto, K., Sato, N., Tsuzuki, M., and Wada, H. (2000) Plant Physiol. 124, 795-804]. We have studied each step of the electron transport in photosystem II of the pgsA mutant to clarify the functional site of PG. Accumulation of Q(A)(-) was indicated by the fast rise of chlorophyll fluorescence yield under continuous and flash illumination. Oxidation of Q(A)(-) by Q(B) plastoquinone was shown to become slow, and Q(A)(-) reoxidation required a few seconds when measured by double flash fluorescence measurements. Thermoluminescence measurements further indicated the accumulation of the S(2)Q(A)(-) state but not of the S(2)Q(B)(-) state following the PG deprivation. These results suggest that the function of Q(B) plastoquinone was inactivated by the PG deprivation. We assume that PG is an indispensable component of the photosystem II reaction center complex to maintain the structural integrity of the Q(B)-binding site. These findings provide the first clear identification of a specific functional site of PG in the photosynthetic reaction center.