Effects of Hydrostatic Pressure on Photosynthetic Systems. I. Preferential Destruction of the O2-Evolving Center |
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Authors: | Yuasa Mitsuyoshi; Ono Taka-aki; Inoue Yorinao |
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Institution: | Solar Energy Research Group, The Institute of Physical and Chemical Research (RIKEN) Wako, Saitama, 351-01 Japan |
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Abstract: | The effects of hydrostatic pressure treatments on the photosyntheticactivities of isolated thylakoids and PSII membranes were studied,and the following results were obtained. (1) The O2-evolvingactivity was selectively inhibited by treatment at 200 MPa andabove, while the electron transport in the PSII reaction center,as measured by the photoreduction of 2,6-dichlorophenolindophenol(DCIP) with 1,5-diphenylcarbazide (DPC), was markedly enhanced.(2) The activity of PSI, as measured by the photoreduction ofmethylviologen with reduced DCIP, was not much affected evenafter treatment at 500 MPa, whereas this electron transportbecame uncoupled from phosphorylation at 200 MPa and above.(3) In pressure-treated PSII membranes, the EPR signal of Y+zbecame photoinducible with the concomitant appearance of anEPR signal for Mn2+. (4) The 33-kDa extrinsic protein was retainedin inhibited PSII membranes, but the 17- and 23-kDa extrinsicproteins were lost. (5) Cross-linking of PSII proteins by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide(EDC) suppressed the pressure-induced inactivation of the evolutionof O2. (6) In pressure-treated PSII membranes, higher concentrationsof DCMU were required to inhibit the photoreduction of DCIP.Features of the pressure-induced inhibition of various reactionsin photosynthetic membranes are discussed on the basis of theseresults.
1On leave from Advanced Research Laboratory, Hitachi Ltd., Hatoyama,Saitama, 350-03 Japan. |
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