title: Specific loss of the extrinsic 18 KDa protein from photosystem II upon heating to 47 degrees C causes inactivation of oxygen evolution likely due to Ca release from the Mn-complex.
abstract: Exposure of Photosystem II (PS II) membrane particles from spinach to a temperature of 47 degrees C caused the rapid release of the 18 kDa protein in parallel to inactivation of oxygen evolution. Previously, it has been suggested that the first heat-jump response involves rapid Ca release from the Mn complex of O2-evolution, followed by the slower release of (2 + 2) MnII ions [Pospisil P et al. (2003) Biophys J 84: 1370-1386]. Here, the predicted biphasic MnII release to the bulk was verified by atomic absorption spectroscopy (AAS). Analysis of laser flash-induced delayed fluorescence transients suggests that the loss of the essential Ca ion from the Mn4Ca complex in the dark is due to the loss of the 18 kDa protein. The S2-state multiline EPR signal of the Mn complex was still generated in heat-treated PS II presumably lacking Ca, but retaining four Mn ions.
authors.affiliation: FB Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Marcos
authors.initials: M
authors.lastname: Barra
authors.forename: Michael
authors.initials: M
authors.lastname: Haumann
authors.forename: Holger
authors.initials: H
authors.lastname: Dau
mesh_terms: D002118:Calcium / Q000378:metabolism*; D004579:Electron Transport; D006358:Hot Temperature; D008345:Manganese / Q000378:metabolism*; D008970:Molecular Weight; D010100:Oxygen / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D018724:Spinacia oleracea / Q000737:chemistry / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D008345:Manganese; D010100:Oxygen; D002118:Calcium