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The pH-dependence of the donor side reactions in Ca2+ -depleted Photosystem II: A role for Ca2+ in the proton expulsion pathway.

Styring, Stenbjörn LU ; Feyzyev, Yashar; Mamedov, Fikret LU ; Babcock, Gerald T. and Hillier, Warwick (2001) In PS2001 Proceedings
Abstract
Removal of Ca2+ from PSII lead to impaired electron transfer from YZ to P680+ and to inhibition of S state transitions which results in a modified stable S2 state (probed by a stable multiline EPR signal) and the induction of the S2YZox state ("split" signal) by illumination at 0° C. We have performed an EPR study on the pH dependence of these reactions in Ca2+-depleted PSII (prepared by citrate treatment at pH 3.0). The stable multiline, the "split" signal and the induction and decay kinetics of YZox over a pH range from 3.5 to 8.0 were investigated. The stable S2 multiline signal showed no significant pH dependence. In contrast, the induction of the "split" signal (two forms of 110 G and 160 G wide were studied) was decreased by 50-60%... (More)
Removal of Ca2+ from PSII lead to impaired electron transfer from YZ to P680+ and to inhibition of S state transitions which results in a modified stable S2 state (probed by a stable multiline EPR signal) and the induction of the S2YZox state ("split" signal) by illumination at 0° C. We have performed an EPR study on the pH dependence of these reactions in Ca2+-depleted PSII (prepared by citrate treatment at pH 3.0). The stable multiline, the "split" signal and the induction and decay kinetics of YZox over a pH range from 3.5 to 8.0 were investigated. The stable S2 multiline signal showed no significant pH dependence. In contrast, the induction of the "split" signal (two forms of 110 G and 160 G wide were studied) was decreased by 50-60% with an apparent pK of 4.5 when the pH was decreased. The decay of the induced YZox at optimal pH values (pH 6-7) shows two kinetic phases with half times of about 0.5 and 20 s. This decay phases became of about 0.1 and 10 s at pH 4.0. Our results indicate that YZox is easier to reduce at low pH values in Ca2+- depleted PSII. Possible donors and the relevance to the proton translocation reactions during S cycle are discussed. (Less)
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type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Photosystem II, calcium, EPR, oxygen evolution
in
PS2001 Proceedings
publisher
CSIRO Publishing
ISBN
CD-ROM - 0643067116
language
English
LU publication?
yes
id
6b616980-4a7e-4524-891c-10e2ae2aee09 (old id 527321)
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http://www.publish.csiro.au/PS2001/cf/search/article.cfm?ID=453065470
date added to LUP
2007-09-25 11:45:32
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2016-04-16 07:51:48
@misc{6b616980-4a7e-4524-891c-10e2ae2aee09,
  abstract     = {Removal of Ca2+ from PSII lead to impaired electron transfer from YZ to P680+ and to inhibition of S state transitions which results in a modified stable S2 state (probed by a stable multiline EPR signal) and the induction of the S2YZox state ("split" signal) by illumination at 0° C. We have performed an EPR study on the pH dependence of these reactions in Ca2+-depleted PSII (prepared by citrate treatment at pH 3.0). The stable multiline, the "split" signal and the induction and decay kinetics of YZox over a pH range from 3.5 to 8.0 were investigated. The stable S2 multiline signal showed no significant pH dependence. In contrast, the induction of the "split" signal (two forms of 110 G and 160 G wide were studied) was decreased by 50-60% with an apparent pK of 4.5 when the pH was decreased. The decay of the induced YZox at optimal pH values (pH 6-7) shows two kinetic phases with half times of about 0.5 and 20 s. This decay phases became of about 0.1 and 10 s at pH 4.0. Our results indicate that YZox is easier to reduce at low pH values in Ca2+- depleted PSII. Possible donors and the relevance to the proton translocation reactions during S cycle are discussed.},
  author       = {Styring, Stenbjörn and Feyzyev, Yashar and Mamedov, Fikret and Babcock, Gerald T. and Hillier, Warwick},
  isbn         = {CD-ROM - 0643067116},
  keyword      = {Photosystem II,calcium,EPR,oxygen evolution},
  language     = {eng},
  publisher    = {ARRAY(0x8dc57e8)},
  series       = {PS2001 Proceedings},
  title        = {The pH-dependence of the donor side reactions in Ca2+ -depleted Photosystem II: A role for Ca2+ in the proton expulsion pathway.},
  year         = {2001},
}