DETECTION OF ONE SLOWLY EXCHANGING SUBSTRATE WATER MOLECULE IN THE S-3 STATE OF PHOTOSYSTEM-II
DETECTION OF ONE SLOWLY EXCHANGING SUBSTRATE WATER MOLECULE IN THE S-3 STATE OF PHOTOSYSTEM-II
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DOI：
10.1073/pnas.92.8.3209
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发表时间：
1995-04-11
影响因子：
11.1
通讯作者：
WYDRZYNSKI, T
中科院分区：
文献类型：
--
作者：
MESSINGER, J;BADGER, M;WYDRZYNSKI, T
通过闪光诱导放氧的同位素交换测量，探讨了光系统II中水氧化催化部位的底物水分子的交换性。与R.Radmer和O.Ollinger[(1986)FEBS Lett]的原始实验相比，构建了一个搅拌样品室，将(H2O)-O-18进样到检测闪光之间的滞后时间缩短了1000倍以上。195、285-289]。我们的数据表明，在光系统II的S-3态中，存在一个慢(t(1/2)约500ms，10℃)和一个快(t(1/2)<；25ms，10℃)交换底物水分子。慢交换与约75kJ/mol的活化能耦合，并从末端锰氧配体的角度进行了讨论，而快交换底物分子可能代表一个不直接结合到锰中心的水分子。
The exchangeability of the substrate water molecules at the catalytic site of water oxidation in photosystem II has been probed by isotope-exchange measurements using mass spectrometric detection of flash-induced oxygen evolution. A stirred sample chamber was constructed to reduce the lag time between injection of (H2O)-O-18 and the detecting flash by a factor of more than 1000 compared to the original experiments by R. Radmer and O. Ollinger [(1986) FEBS Lett. 195, 285-289]. Our data show that there is a slow (t(1/2) approximate to 500 ms, 10 degrees C) and a fast (t(1/2) < 25 ms, 10 degrees C) exchanging substrate water molecule in the S-3 State of photosystem II. The slow exchange is coupled with an activation energy of about 75 kJ/mol and is discussed in terms of a terminal manganese oxo ligand, while the faster exchanging substrate molecule may represent a water molecule not directly bound to the manganese center.