Chloride binding to photosystem II in the dark is in slow exchange.
We have studied the 35Cl- NMR line broadening in the presence of photosystem II (PS II) membranes from spinach in the dark. In the presence of NH3 (which other work has shown to competitively inhibit chloride binding to PS II) we observed no decrease in 35 Cl- linewidths. We conclude that binding of Cl- to the O2 evolving center in PS II in the dark (previously demonstrated by EPR) is in slow exchange on the NMR timescale. We assign the observed line broadening to interaction with non-specific binding sites and with free paramagnetics.
Shachar-Hill
Y
Y
Dept of Chemistry, Yale University, New Haven, CT 06511.
Beck
W F
WF
Brudvig
G W
GW
D002712:Chlorides / Q000032:analysis / Q000378:metabolism*; D002734:Chlorophyll / Q000032:analysis*; D003624:Darkness; D004578:Electron Spin Resonance Spectroscopy; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes; D009682:Magnetic Resonance Spectroscopy; D010100:Oxygen / Q000032:analysis; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000032:analysis*; D010944:Plants / Q000032:analysis*; D011485:Protein Binding
D002712:Chlorides; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D010100:Oxygen