Advanced

Molecular interference of Cd2+ with Photosystem II

Sigfridsson Clauss, Kajsa LU ; Bernat, Gabor LU ; Mamedov, Fikret LU and Styring, Stenbjörn LU (2004) In Biochimica et Biophysica Acta - Bioenergetics 1659(1). p.19-31
Abstract
Many heavy metals inhibit electron transfer reactions in Photosystem II (PSII). Cd2+ is known to exchange, with high affinity in a slow reaction, for the Ca2+ cofactor in the Ca/Mn cluster that constitutes the oxygen-evolving center. This results in inhibition of photosynthetic oxygen evolution. There are also indications that Cd2+ binds to other sites in PSII, potentially to proton channels in analogy to heavy metal binding in photosynthetic reaction centers from purple bacteria. In search for the effects of Cd2+-binding to those sites, we have studied how Cd2+ affects electron transfer reactions in PSII after short incubation times and in sites, which interact with Cd2+ with low affinity. Overall electron transfer and partial electron... (More)
Many heavy metals inhibit electron transfer reactions in Photosystem II (PSII). Cd2+ is known to exchange, with high affinity in a slow reaction, for the Ca2+ cofactor in the Ca/Mn cluster that constitutes the oxygen-evolving center. This results in inhibition of photosynthetic oxygen evolution. There are also indications that Cd2+ binds to other sites in PSII, potentially to proton channels in analogy to heavy metal binding in photosynthetic reaction centers from purple bacteria. In search for the effects of Cd2+-binding to those sites, we have studied how Cd2+ affects electron transfer reactions in PSII after short incubation times and in sites, which interact with Cd2+ with low affinity. Overall electron transfer and partial electron transfer were studied by a combination of EPR spectroscopy of individual redox components, flash-induced variable fluorescence and steady state oxygen evolution measurements. Several effects of Cd2+ were observed: (i) the amplitude of the flash-induced variable fluorescence was lost indicating that electron transfer from Y-Z to P-680(+) was inhibited; (ii) Q(A)(-) to Q(B) electron transfer was slowed down; (iii) the S-2 state multiline EPR signal was not observable; (iv) steady state oxygen evolution was inhibited in both a high-affinity and a low-affinity site; (v) the spectral shape of the EPR signal from Q(A)(-)Fe(2+) was modified but its amplitude was not sensitive to the presence of Cd2+. In addition, the presence of both Ca2+ and DCMU abolished Cd2+-induced effects partially and in different sites. The number of sites for Cd2+ binding and the possible nature of these sites are discussed. (C) 2004 Elsevier B.V. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biochimica et Biophysica Acta - Bioenergetics
volume
1659
issue
1
pages
19 - 31
publisher
Elsevier
external identifiers
  • wos:000224938900002
  • pmid:15511524
  • scopus:7244223640
ISSN
0005-2728
DOI
10.1016/j.bbabio.2004.07.003
language
English
LU publication?
yes
id
e165ed32-fabc-43e7-b058-c32cdbf9b7be (old id 138662)
date added to LUP
2007-07-06 15:10:16
date last changed
2017-11-19 04:10:14
@article{e165ed32-fabc-43e7-b058-c32cdbf9b7be,
  abstract     = {Many heavy metals inhibit electron transfer reactions in Photosystem II (PSII). Cd2+ is known to exchange, with high affinity in a slow reaction, for the Ca2+ cofactor in the Ca/Mn cluster that constitutes the oxygen-evolving center. This results in inhibition of photosynthetic oxygen evolution. There are also indications that Cd2+ binds to other sites in PSII, potentially to proton channels in analogy to heavy metal binding in photosynthetic reaction centers from purple bacteria. In search for the effects of Cd2+-binding to those sites, we have studied how Cd2+ affects electron transfer reactions in PSII after short incubation times and in sites, which interact with Cd2+ with low affinity. Overall electron transfer and partial electron transfer were studied by a combination of EPR spectroscopy of individual redox components, flash-induced variable fluorescence and steady state oxygen evolution measurements. Several effects of Cd2+ were observed: (i) the amplitude of the flash-induced variable fluorescence was lost indicating that electron transfer from Y-Z to P-680(+) was inhibited; (ii) Q(A)(-) to Q(B) electron transfer was slowed down; (iii) the S-2 state multiline EPR signal was not observable; (iv) steady state oxygen evolution was inhibited in both a high-affinity and a low-affinity site; (v) the spectral shape of the EPR signal from Q(A)(-)Fe(2+) was modified but its amplitude was not sensitive to the presence of Cd2+. In addition, the presence of both Ca2+ and DCMU abolished Cd2+-induced effects partially and in different sites. The number of sites for Cd2+ binding and the possible nature of these sites are discussed. (C) 2004 Elsevier B.V. All rights reserved.},
  author       = {Sigfridsson Clauss, Kajsa and Bernat, Gabor and Mamedov, Fikret and Styring, Stenbjörn},
  issn         = {0005-2728},
  language     = {eng},
  number       = {1},
  pages        = {19--31},
  publisher    = {Elsevier},
  series       = {Biochimica et Biophysica Acta - Bioenergetics},
  title        = {Molecular interference of Cd2+ with Photosystem II},
  url          = {http://dx.doi.org/10.1016/j.bbabio.2004.07.003},
  volume       = {1659},
  year         = {2004},
}