The pH-dependence of the donor side reactions in Ca2+ -depleted Photosystem II: A role for Ca2+ in the proton expulsion pathway.
(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)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/527321
- author
- Styring, Stenbjörn LU ; Feyzyev, Yashar ; Mamedov, Fikret LU ; Babcock, Gerald T. and Hillier, Warwick
- organization
- publishing date
- 2001
- 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}}, }