title: Interaction of bicarbonate with the manganese-stabilizing protein of photosystem II.
abstract: The effect of reversible removal of HCO(3)(-) on structural re-arrangements in the Mn-stabilizing protein (MSP) of photosystem II, isolated from pea leaves, was studied using measurements of characteristic alterations in fluorescence of hydrophobic probe 8-anilino-1-naphthalene-sulfonic acid (ANS). It was shown that the treatments capable of removal of HCO(3)(-) (or CO(2)) from possible binding sites in MSP (pH lowering from 6.5 to 3.5, addition of a structurally similar anion HCO(3)(-) in concentration 1-20mM or air evacuation at pH 3.5) result in a significant (up to 370%) increase of ANS fluorescence (indicative of structural changes in MSP), whereas HCO(3)(-) lowers the ANS fluorescence to the initial level observed in untreated protein at pH 6.5. Since the effects are revealed at (sub)micromolar concentrations of HCO(3)(-), the specific high-affinity binding of HCO(3)(-) (or CO(2)) to MSP (required for its native structure preservation) is proposed. Possible bicarbonate binding sites and its physiological role within the water-oxidizing complex of photosystem II are discussed.
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia. nikitishena@mail.ru
authors.forename: Olga V
authors.initials: OV
authors.lastname: Pobeguts
authors.forename: Tatiana N
authors.initials: TN
authors.lastname: Smolova
authors.forename: Dmitry S
authors.initials: DS
authors.lastname: Timoshevsky
authors.forename: Vyacheslav V
authors.initials: VV
authors.lastname: Klimov
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D001639:Bicarbonates / Q000737:chemistry*; D001665:Binding Sites; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008345:Manganese / Q000737:chemistry*; D018532:Pisum sativum / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D001639:Bicarbonates; D005456:Fluorescent Dyes; D045332:Photosystem II Protein Complex; D008345:Manganese