THE RATE OF REDUCTION OF OXIDIZED REDOX-ACTIVE TYROSINE, Z+, BY EXOGENOUS MN2+ IS SLOWED IN A SITE-DIRECTED MUTANT, AT ASPARTATE 170 OF POLYPEPTIDE D1 OF PHOTOSYSTEM-II, INACTIVE FOR PHOTOSYNTHETIC OXYGEN EVOLUTION
THE RATE OF REDUCTION OF OXIDIZED REDOX-ACTIVE TYROSINE, Z+, BY EXOGENOUS MN2+ IS SLOWED IN A SITE-DIRECTED MUTANT, AT ASPARTATE 170 OF POLYPEPTIDE D1 OF PHOTOSYSTEM-II, INACTIVE FOR PHOTOSYNTHETIC OXYGEN EVOLUTION
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DOI：
10.1016/0005-2728(92)90196-9
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发表时间：
1992-07-17
期刊：
影响因子：
--
通讯作者：
NIXON, PJ
中科院分区：
文献类型：
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作者：
DINER, BA;NIXON, PJ
聚囊藻PCC 6803的光系统II多肽D1的Asp-170的11个不同的位点导向突变体显示出不同程度的光驱动水氧化活性，这取决于取代的性质（Nixon， P.J.和Diner， ba .（1992）生化31,942-948）。这些范围从最活跃的谷氨酸，具有接近野生型的氧演化速率到完全不活跃的丝氨酸和丙氨酸。从野生型和D1-Asp170Ser中分离的光系统II核心配合物缺乏负责水氧化的四核Mn簇，比较了Mn2+对光氧化氧化活性酪氨酸Z+的还原动力学。Z+还原速率对Mn2+浓度的依赖性在野生型中表现为混合的一阶和二阶行为，而在突变体中表现为单独的二阶行为。野生型和突变型复合物的二级速率常数分别为3.1.10(7)M-1 s-1和5.5.10(5)M-1 s-1。这些速率常数的比值与先前测定的Mn2+阻断电荷复合的K(m)值一致。因此，d1 -天冬氨酸170与Mn2+氧化的便利途径有关，这很可能包括参与光系统II反应中心的高亲和力金属结合位点（Mn2+和/或Mn3+）。
Eleven different site-directed mutants at Asp-170 of Photosystem II polypeptide D1 of Synechocystis PCC 6803 show varying degrees of activity for light-driven water oxidation depending on the nature of the substitution (Nixon, P.J. and Diner, B.A. (1992) Biochemistry 31, 942-948). These range from the most active, glutamate, with near wild-type rates of oxygen evolution to the totally inactive serine and alanine. Photosystem II core complexes lacking the tetranuclear Mn cluster responsible for water oxidation and isolated from wild-type and D1-Asp170Ser, were compared with respect to the kinetics of reduction by Mn2+ of the photooxidized redox-active tyrosine, Z+. The dependence of the rate of reduction of Z+ on the Mn2+ concentration shows mixed first and second-order behavior in the case of the wild-type and second-order behavior alone in the case of the mutant. The second-order rate constants for the wild-type and mutant complexes were 3.1.10(7) M-1 s-1 and 5.5.10(5) M-1 s-1, respectively. The ratio of these rate constants is consistent with the K(m) values determined earlier for the blockage of charge recombination by Mn2+. D1-Aspartate 170 is therefore implicated in a facilitated pathway for the oxidation of Mn2+, which most likely includes participation in a high-affinity metal binding site (Mn2+ and/or Mn3+) in the Photosystem II reaction center.