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Bicarbonate is a native cofactor for assembly of the manganese cluster of the photosynthetic water oxidizing complex. Kinetics of reconstitution of O2 evolution by photoactivation

Baranov, S V ; Tyryshkin, A M ; Katz, D ; Dismukes, G C ; Ananyev, G M ; Klimov, V V

Biochemistry, 24 February 2004, Vol.43(7), pp.2070-9 [Periódico revisado por pares]

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  • Título:
    Bicarbonate is a native cofactor for assembly of the manganese cluster of the photosynthetic water oxidizing complex. Kinetics of reconstitution of O2 evolution by photoactivation
  • Autor: Baranov, S V ; Tyryshkin, A M ; Katz, D ; Dismukes, G C ; Ananyev, G M ; Klimov, V V
  • Assuntos: Protein Processing, Post-Translational ; Bicarbonates -- Chemistry ; Manganese -- Chemistry ; Oxygen -- Chemistry ; Photosystem II Protein Complex -- Chemistry ; Plant Proteins -- Chemistry ; Water -- Chemistry
  • É parte de: Biochemistry, 24 February 2004, Vol.43(7), pp.2070-9
  • Descrição: Assembly of the inorganic core (Mn(4)O(x)Ca(1)Cl(y)) of the water oxidizing enzyme of oxygenic photosynthesis generates O(2) evolution capacity via the photodriven binding and photooxidation of the free inorganic cofactors within the cofactor-depleted enzyme (apo-WOC-PSII) by a process called photoactivation. Using in vitro photoactivation of spinach PSII membranes, we identify a new lower affinity site for bicarbonate interaction in the WOC. Bicarbonate addition causes a 300% stimulation of the rate and a 50% increase in yield of photoassembled PSII centers when using Mn(2+) and Ca(2+) concentrations that are 10-50-fold larger range than previously examined. Maintenance of a fixed Mn(2+)/Ca(2+) ratio (1:500) produces the fastest rates and highest yields of photoactivation, which has implications for intracellular cofactor homeostasis. A two-step (biexponential) model is shown to accurately fit the assembly kinetics over a 200-fold range of Mn(2+) concentrations. The first step, the binding...
  • Idioma: Inglês

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