Spectroscopic evidence from site-directed mutants of Synechocystis PCC6803 in favor of a close interaction between histidine 189 and redox-active tyrosine 160, both of polypeptide D2 of the photosystem II reaction center.
Spectroscopic evidence from site-directed mutants of Synechocystis PCC6803 in favor of a close interaction between histidine 189 and redox-active tyrosine 160, both of polypeptide D2 of the photosystem II reaction center.
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来自集胞藻 PCC6803 定点突变体的光谱证据支持组氨酸 189 和氧化还原活性酪氨酸 160 之间的密切相互作用，两者都是光系统 II 反应中心的多肽 D2。
DOI：
10.1021/bi00212a045
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Diner,BA
中科院分区：
文献类型：
--
作者：
Tang,XS;Chisholm,DA;Dismukes,GC;Brudvig,GW;Diner,BA
修订稿于 1993 年 9 月 29 日收到*摘要：含氧光合作用的光系统 II 的反应中心包含两个氧化还原活性酪氨酸，称为 Z 和 D，每个酪氨酸都可以充当氧化初级电子供体 Pego"1- 的电子供体。这些酪氨酸位于两个同源多肽 DI 和 D2 各自的第三跨膜螺旋上的同源位置，构成已提出，多肽 D2 的酪氨酸 D 在氧化后将其酚质子转变为附近的碱性氨基酸残基，形成中性自由基。模型研究指出 His 190（菠菜编号）可能是该碱性残基的候选者。从这三个突变体中分离的 PSII 核心复合物显示出改变的暗稳定 EPR 信号，线宽变窄 (11-13 G)，g 值为 2.0046，而不是正常的 D’EPR 信号（菠菜 His 190 的集胞藻同源物）。 Hisl89Gln、His189Asp 和 Hisl89Leu 突变体分别为 2.0043 和 2.0042，尽管线宽减小，但这些 EPR 信号显示出与正常 D' 信号相似的 g 值和微波功率饱和特性。此外，这些突变体之一在光系统 II 反应中心酪氨酸的 3 和 5 位置处的特异性氘化导致超精细的损失。 EPR 信号的结构，证明信号确实来自于这些酪氨酸自由基的质子 ENDOR 研究表明，在野生型菌株中观察到的一种超精细耦合成分在所有三种突变体中消失，在 DzO 中孵育时，这种超精细耦合消失，表明它源自可交换质子，很可能通过氢键与 D' 相互作用。提供了强有力的实验证据，支持光系统 II 的 D2 多肽中 Hisl 89 和 Tyrl60 之间的密切相互作用。这一观察结果为这样的模型提供了支持：His 189 的咪唑氮在 D 氧化后接受 Tyrl60 的酚质子，与中性酪氨酰自由基的酚氧形成反向氢键。绿色植物、藻类和蓝细菌的光系统 II 反应中心催化光诱导的氧化。反应中心主要由两个完整的膜多肽（DI 和 D2）组成，它们分别与紫色光合细菌反应中心的 L 和 M 亚基具有区域同源性（Trebst，1986；Nanba & Satoh，1987；Michel & Deisenhofer，1988；Tang 等，1990）。
Revised Manuscript Received September 29, 1993* abstract: The reaction center of photosystem II of oxygenic photosynthesis contains two redox-active tyrosines called Z and D, each of which can act as an electron donor to the oxidized primary electron donor, Pego" 1-. These tyrosines are located in homologous positions on the third transmembrane-helix of each of the two homologous polypeptides, DI and D2, that comprise the reaction center. Tyrosine D of polypeptide D2 has been proposed, upon oxidation, to give up its phenolic proton to a nearby basic amino acid residue, forming a neutral radical. Modeling studies have pointed to His 190 (spinach numbering) as a likely candidate for this basic residue. As a test of this hypothesis, we have constructed three site-directed mutations in the D2 polypeptide of the cyanobacterium Synechocystis sp. PCC6803. Hisl 89 (the Synechocystis homologue of His 190 of spinach) has been replaced by glutamine, aspartate, or leucine. Instead of the normal D’EPR signal (g= 2.0046; line width 16-19 G), PSII core complexes isolated from these three mutants show an altered dark-stable EPR signal with a narrowed line width (11-13 G), and g values of 2.0046, 2.0043, and 2.0042 for the Hisl89Gln, His 189Asp, and Hisl89Leu mutants, respectively. Despite the reduced line width, these EPR signalsshow g values and microwave-powersaturation properties similar to the normal D ‘signal. Furthermore, specific deuterationin one of those mutants at the 3 and 5 positions of the phenol ring of the photosystem II reaction center tyrosines results in a loss of hyperfine structure of the EPR signal, proving that the signal indeed arises from tyrosine. Proton-ENDOR studies of these tyrosine radicals show that one hyperfine coupling component of 3.5-3.6 MHz, observed in the wild-type strain disappears in all three mutants. Upon incubation of wild-type photosystem II core complexes in DzO, this hyperfine coupling is lost, indicating that it originates from an exchangeable proton, most likely interacting with D'through a hydrogen bond. These results provide strong experimental evidence in favor of a close interaction between Hisl 89 and Tyrl60 in the D2 polypeptide of photosystem II. This observation provides support for a model in which an imidazole nitrogen of His 189 accepts the phenolicproton of Tyrl60 upon oxidation of D, forming a back hydrogen bond to the phenolic oxygen of the neutral tyrosyl radical.The photosystem II reaction center of green plants, algae, and cyanobacteria catalyzes thelight-induced oxidation of water and reduction of plastoquinone. The reaction center consists principally of two integral membrane polypeptides (DI and D2) that show regional homologies to the L and M subunits, respectively, of the purple photosynthetic bacteria reaction center (Trebst, 1986; Nanba & Satoh, 1987; Michel & Deisenhofer, 1988; Tang et al., 1990). The DI and D2
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DOI：
10.1111/j.1749-6632.1975.tb41534.x
发表时间：
1975-01-01
影响因子：
5.2
作者：
FEHER, G;HOFF, AJ;ACKERSON, LC
通讯作者：
ACKERSON, LC
光系统II中酪氨酰供体D的Eseem研究
DOI：
10.1007/978-94-009-0511-5_110
发表时间：
1990
影响因子：
1.4
作者：
R. Evelo;S. Dikanov;A. Hoff
通讯作者：
A. Hoff
光系统 II 中的酪氨酸自由基和相关模型化合物。
DOI：
--
发表时间：
1990
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Barry,BA;el-Deeb,MK;Sandusky,PO;Babcock,GT
通讯作者：
Babcock,GT
菠菜分离和部分表征中光系统 II 反应中心的 D1-D2 复合物
影响因子：
3.5
作者：
Xiao;K. Fushimi;K. Satoh
通讯作者：
K. Satoh
影响因子：
2.9
作者：
HOGANSON, CW;BABCOCK, GT
通讯作者：
BABCOCK, GT