title: Oxygen evolution in the absence of the 33-kilodalton manganese-stabilizing protein.
abstract: There has been a considerable amount of controversy concerning the ability of photosystem II to evolve oxygen in the absence of the 33-kDa, manganese-stabilizing protein. Early reports indicated that some capacity for oxygen evolution existed in manganese-stabilizing protein-depleted membranes while more recent studies have suggested that the observed oxygen evolution activity arose from residual manganese-stabilizing protein present in the salt-washed preparations. In this paper, it is conclusively demonstrated that significant rates of steady-state oxygen evolution are observed in oxygen-evolving photosystem II membranes in the absence of detectable quantities of the manganese-stabilizing protein. More then 99% of the manganese-stabilizing protein was removed by either one CaCl2 or two NaCl-urea washes. The amount of manganese-stabilizing protein removed was quantified immunologically using mouse polyclonal antibodies. Oxygen evolution rates of 115-140 mumol of O2 (mg of Chl)-1 h-1 were observed in the NaCl-urea-washed preparations. These rates represent about 24% of the rate observed in untreated membranes [450-600 mumol of O2 (mg of Chl)-1 h-1]. Somewhat lower, although still significant rates were observed in the CaCl2-washed preparations. Optimal rates of oxygen-evolving activity in NaCl-urea-washed membranes which are devoid of the manganese-stabilizing protein required high concentrations of calcium and chloride.
authors.affiliation: Department of Botany, Louisiana State University, Baton Rouge 70803.
authors.forename: T M
authors.initials: TM
authors.lastname: Bricker
mesh_terms: D007700:Kinetics; D008345:Manganese / Q000737:chemistry*; D008667:Metalloproteins / Q000737:chemistry*; D008970:Molecular Weight; D010100:Oxygen / Q000737:chemistry*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000737:chemistry*; D011506:Proteins
chemical_list: D008667:Metalloproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011506:Proteins; C054266:photosystem II manganese-stabilizing protein; D008345:Manganese; D010100:Oxygen