Inhibition of Photosynthetic Energy Conversion by Cupric Ion: Evidence for Cu(m=^2)⁺-Coupling Factor 1 Interaction

This study describes a specific Cu2+ and light-dependent inhibition of spinach (Spinacia oleracea L.) chloroplast reactions involving coupling factor 1 function. A primary effect is an inhibition of photophosphorylation induced by illumination of Class II chloroplasts with micromolar Cu2+ and pyocya...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1982-05, Vol.69 (5), p.1040-1045
Main Authors: Uribe, Ernest G., Benjamin Stark
Format: Article
Language:English
Subjects:
Adenosine triphosphatases
Chloroplasts
Gels
Nucleotides
Phosphorylation
Photoinhibition
Photophosphorylation
Proton pumps
Protons
Spinach
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Summary:This study describes a specific Cu2+ and light-dependent inhibition of spinach (Spinacia oleracea L.) chloroplast reactions involving coupling factor 1 function. A primary effect is an inhibition of photophosphorylation induced by illumination of Class II chloroplasts with micromolar Cu2+ and pyocyanine in the absence of ADP, Mg2+, and $\text{HPO}_{4}{}^{2-}$. The inhibition, which is dependent on free Cu2+ as indicated by protection by ethylene diamine tetraacetic acid and dithiothreitol, requires illumination (electron flow) for establishment of the specific inhibition to be noted. Protection is also afforded by uncouplers and some partial protection is provided by micromolar concentrations of ADP and ATP. The data strongly suggest that Cu2+ causes an O2-independent oxidation of sulfhydryl groups on coupling factor 1, which are essential to catalytic function. This conclusion is supported by the reduction of energy-dependent 3H-N-ethylmaleimide labeling of the γ subunit of coupling factor 1 by the Cu2+-light pretreatment.
ISSN:0032-0889
1532-2548