期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 108, 期 19, 页码 8054-8058出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1100173108
关键词
photosynthesis; photochemical reaction
资金
- Japanese Society for the Promotion of Science [17GS0314]
- Ministry of Education of Japan [21570038, 22370017]
- Japan Science and Technology Agency
- Russian Foundation for Basic Research [11-04-01389a, 11-04-92690a]
- Russian Ministry of Science and Education [16.740.11.0176]
- Russian Academy of Sciences
- Grants-in-Aid for Scientific Research [21570038, 22370017] Funding Source: KAKEN
In a previous study, we measured the redox potential of the primary electron acceptor pheophytin (Phe) a of photosystem (PS) II in the chlorophyll d-dominated cyanobacterium Acaryochloris marina and a chlorophyll a-containing cyanobacterium, Synechocystis. We obtained the midpoint redox potential (E-m) values of -478 mV for A. marina and -536 mV for Synechocystis. In this study, we measured the redox potentials of the primary electron acceptor quinone molecule (Q(A)), i.e., Em(Q(A)/Q(A)(-)), of PS II and the energy difference between [P680.Phe a(-).Q(A)] and [P680.Phe a.Q(A)(-)], i.e., Delta G(PhQ). The E-m(Q(A)/Q(A)(-)) of A. marina was determined to be +64 mV without the Mn cluster and was estimated to be -66 to -86 mV with a Mn-depletion shift (130-150 mV), as observed with other organisms. The E-m(Phe a/Phe a(-)) in Synechocystis was measured to be -525 mV with the Mn cluster, which is consistent with our previous report. The Mn-depleted downshift of the potential was measured to be approximately -77 mV in Synechocystis, and this value was applied to A. marina (-478mV); the E-m(Phe a/Phe a(-)) was estimated to be approximately -401 mV. These values gave rise to a Delta G(PhQ) of -325 mV for A. marina and -383 mV for Synechocystis. In the two cyanobacteria, the energetics in PS II were conserved, even though the potentials of Q(A)(-) and Phe a(-) were relatively shifted depending on the special pair, indicating a common strategy for electron transfer in oxygenic photosynthetic organisms.
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