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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)
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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author
; ; ; and
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Photosystem II, calcium, EPR, oxygen evolution
host publication
PS2001 Proceedings
publisher
CSIRO Publishing
ISBN
CD-ROM - 0643067116
language
English
LU publication?
yes
id
6b616980-4a7e-4524-891c-10e2ae2aee09 (old id 527321)
alternative location
http://www.publish.csiro.au/PS2001/cf/search/article.cfm?ID=453065470
date added to LUP
2016-04-04 10:24:51
date last changed
2018-11-21 20:58:37
@inproceedings{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}},
  booktitle    = {{PS2001 Proceedings}},
  isbn         = {{CD-ROM - 0643067116}},
  keywords     = {{Photosystem II; calcium; EPR; oxygen evolution}},
  language     = {{eng}},
  publisher    = {{CSIRO Publishing}},
  title        = {{The pH-dependence of the donor side reactions in Ca2+ -depleted Photosystem II: A role for Ca2+ in the proton expulsion pathway.}},
  url          = {{http://www.publish.csiro.au/PS2001/cf/search/article.cfm?ID=453065470}},
  year         = {{2001}},
}