Competitive inhibition of electron donation to photosystem 1 by metal-substituted plastocyanin.
Biochim Biophys Acta
; 1777(9): 1116-21, 2008 Sep.
Article
em En
| MEDLINE
| ID: mdl-18445472
ABSTRACT
The electron transfer from wild-type spinach plastocyanin (Pc) to photosystem 1 has been studied by flash-induced absorption changes at 830 nm. The decay kinetics of photo-oxidized P700 are drastically slower in the presence of Ag(I)-substituted Pc, while addition of Zn(II)-substituted Pc has a weaker effect. The metal-substituted forms of Pc act as competitive inhibitors of the reaction between normal, Cu-containing, Pc and P700. The inhibition constants obtained from an analysis of the kinetic data were 30 and 410 microM for Ag(I)- and Zn(II)-substituted Pc, respectively. When the Gly8Asp mutant form of Pc was used instead of the wild-type form, the corresponding values were found to be 77 and 442 microM. If the Ag- and Zn-derivatives can be considered as structural mimics of reduced and oxidized CuPc, respectively, our results imply that there is a redox-induced decrease in the affinity between Pc and photosystem 1 that follows the electron donation to P700. Our data also imply that the Gly8Asp mutation can diminish the magnitude of this change. The findings reported here are consistent with a reaction mechanism where the electron transfer in the complex between Pc and photosystem 1 is assumed to be reversible.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Plastocianina
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Spinacia oleracea
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Complexo de Proteína do Fotossistema I
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Elétrons
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Metais
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article