期刊
BIOCHEMISTRY
卷 52, 期 28, 页码 4748-4757出版社
AMER CHEMICAL SOC
DOI: 10.1021/bi301699h
关键词
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资金
- Ministry of Education, Culture, Sports, Science and Technology [23657099, 24000018, 24107003, 25291033]
- Biotechnology and Biological Sciences Research Council [BB/C507037]
- Grants-in-Aid for Scientific Research [23657099, 24000018, 24107003] Funding Source: KAKEN
- Biotechnology and Biological Sciences Research Council [BB/C507037/1] Funding Source: researchfish
Photosynthetic water oxidation in plants and cyanobacteria is catalyzed by a Mn4CaO5 cluster within the photosystem II (PSII) protein complex. Two Cl(-)ions bound near the Mn4CaO5 cluster act as indispensable cofactors, but their functional roles remain to be clarified. We have investigated the role of the Cl- ion interacting with D2-K317 (designated Cl-1) by Fourier transform infrared spectroscopy (FTIR) analysis of the D2-K317R mutant of Synechocystis sp. PCC 6803 in combination with Cl-/NO3- replacement. The D2-K317R mutation perturbed the bands in the regions of the COO- stretching and backbone amide vibrations in the FTIR difference spectrum upon the S-1 -> S-2 transition. In addition, this mutation altered the N-15 isotope-edited NO(3)(-)(-)bands in the spectrum of NO3--treated PSII. These results provide the first experimental evidence that the Cl-1 site is coupled with the Mn4CaO5 cluster and its interaction is affected by the S-1 -> S-2 transition. It was also shown that a negative band at 1748 cm(-1) arising from COOH group(s) was altered to a positive intensity by the D2-K317R mutation as well as by NO3- treatment, suggesting that the Cl-1 site affects the pK(a) of COOH/COO- group(s) near the Mn4CaO5 cluster in a common hydrogen bond network. Together with the observation that the efficiency of the S-3 -> S-0 transition significantly decreased in the core complexes of D2-K317R upon moderate dehydration, it is suggested that D2-K317 and Cl-1 are involved in a proton transfer pathway from the Mn4CaO5 cluster to the lumen, which functions in the S-3 -> S-0 transition.
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