کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10795467 | 1052586 | 2014 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae
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کلمات کلیدی
موضوعات مرتبط
علوم زیستی و بیوفناوری
علوم کشاورزی و بیولوژیک
دانش گیاه شناسی
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چکیده انگلیسی
The binding affinity of the two substrate-water molecules to the water-oxidizing Mn4CaO5 catalyst in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae was studied in the S2 and S3 states by the exchange of bound 16O-substrate against 18O-labeled water. The rate of this exchange was detected via the membrane-inlet mass spectrometric analysis of flash-induced oxygen evolution. For both redox states a fast and slow phase of water-exchange was resolved at the mixed labeled m/z 34 mass peak: kf = 52 ± 8 sâ 1 and ks = 1.9 ± 0.3 sâ 1 in the S2 state, and kf = 42 ± 2 sâ 1 and kslow = 1.2 ± 0.3 sâ 1 in S3, respectively. Overall these exchange rates are similar to those observed previously with preparations of other organisms. The most remarkable finding is a significantly slower exchange at the fast substrate-water site in the S2 state, which confirms beyond doubt that both substrate-water molecules are already bound in the S2 state. This leads to a very small change of the affinity for both the fast and the slowly exchanging substrates during the S2 â S3 transition. Implications for recent models for water-oxidation are briefly discussed.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biochimica et Biophysica Acta (BBA) - Bioenergetics - Volume 1837, Issue 8, August 2014, Pages 1257-1262
Journal: Biochimica et Biophysica Acta (BBA) - Bioenergetics - Volume 1837, Issue 8, August 2014, Pages 1257-1262
نویسندگان
HÃ¥kan Nilsson, Tomasz Krupnik, Joanna Kargul, Johannes Messinger,