title: Redox interaction of Mn-bicarbonate complexes with reaction centres of purple bacteria.
abstract: It is found that dark reduction of photooxidized primary electron donor P870+ in reaction centres from purple anoxygenic bacteria (two non-sulphur Fe-oxidizing Rhodovulum iodosum and Rhodovulum robiginosum, Rhodobacter sphaeroides R-26 and sulphur alkaliphilic Thiorhodospira sibirica) is accelerated upon the addition of Mn2+ jointly with bicarbonate (30-75 mM). The effect is not observed if Mn2+ and HCO3(-) have been replaced by Mg2+ and HCO2(-), respectively. The dependence of the effect on bicarbonate concentration suggests that formation of Mn2+-bicarbonate complexes, Mn(HCO3)+ and/or Mn(HCO3)2, is required for re-reduction of P870+ with Mn2+. The results are considered as experimental evidence for a hypothesis on possible participation of Mn-bicarbonate complexes in the evolutionary origin of oxygenic photosynthesis in the Archean era.
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
authors.forename: A A
authors.initials: AA
authors.lastname: Khorobrykh
authors.forename: V V
authors.initials: VV
authors.lastname: Terentyev
authors.forename: S K
authors.initials: SK
authors.lastname: Zharmukhamedov
authors.forename: V V
authors.initials: VV
authors.lastname: Klimov
mesh_terms: D001639:Bicarbonates / Q000737:chemistry*; D007700:Kinetics; D008345:Manganese / Q000737:chemistry*; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001639:Bicarbonates; D045322:Photosynthetic Reaction Center Complex Proteins; D008345:Manganese