title: Chloride-depletion effects in the calcium-deficient oxygen-evolving complex of photosystem II.
abstract: The effects of Cl-depletion in photosystem II (PS-II)-enriched membranes have been investigated by electron paramagnetic resonance (EPR) spectroscopy after removal of the 17- and 23-kDa polypeptides and depletion of Ca2+ by NaCl treatment. When the salt treatment was done in the presence of a high concentration (5 mM) of the chelator [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA), a modified dark-stable multiline signal was observed from the S2 state and a 13 mT wide S3 signal could be generated by illumination at 0 degrees C as reported previously for experiments conducted under these conditions [Boussac, A., Zimmermann, J.-L., & Rutherford, A. W. (1990) FEBS Lett. 277, 69-74]. The modified S2 multiline signal was lost after a further Cl- depletion in the presence of a low EGTA concentration (50 microM). Upon Cl- reconstitution, a normal S2 multiline signal could be generated by continuous illumination at 200 K. In contrast, a lowering of the EGTA concentration (50 microM) alone, in the presence of Cl- (30 mM), had no effect on the modified S2 multiline signal. These results indicate that the modification of S2 is due to binding of the chelator to PS-II and that Cl- stabilizes the chelator binding. When Cl- depletion in Ca(2+)-depleted PS-II was done in the presence of a high concentration of EGTA (5 mM), the modified S2 multiline signal disappeared but was regenerated by Cl- reconstitution in darkness. These results indicate that when Cl- depletion is done to the EGTA-modified PS-II, the S2 multiline signal disappears but the S2 state remains stable in the dark.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Section de Bioénergétique (URA CNRS 1290), Département de Biologie Cellulaire et Moléculaire, CEA Saclay, Gif-sur-Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: van Vliet
authors.forename: A
authors.initials: A
authors.lastname: Boussac
authors.forename: A W
authors.initials: AW
authors.lastname: Rutherford
mesh_terms: D017738:Alkanesulfonic Acids / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D002951:Citrates / Q000494:pharmacology; D011756:Diphosphates / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D008970:Molecular Weight; D009025:Morpholines / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D012015:Reference Standards
chemical_list: D017738:Alkanesulfonic Acids; D002712:Chlorides; D002951:Citrates; D011756:Diphosphates; D009025:Morpholines; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C004550:2-(N-morpholino)ethanesulfonic acid; D004533:Egtazic Acid; D004492:Edetic Acid; D010100:Oxygen; D002118:Calcium