Additive Effect of Mutations Affecting the Rate of Phylloquinone Reoxidation and Directionality of Electron Transfer within Photosystem I†
| Autor: | Stefano Santabarbara, Fabrice Rappaport, Martin Byrdin, Kevin Redding, Feifei Gu, Audrius Jasaitis |
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| Rok vydání: | 2008 |
| Předmět: |
Models
Molecular Photosynthetic reaction centre Mutant Chlamydomonas reinhardtii medicine.disease_cause Photosystem I Biochemistry Electron Transport Electron transfer medicine Animals Directionality Physical and Theoretical Chemistry Mutation Photosystem I Protein Complex biology Chemistry Vitamin K 1 General Medicine biology.organism_classification Acceptor Protein Structure Tertiary Kinetics Crystallography Spectrophotometry Oxidation-Reduction |
| Zdroj: | Photochemistry and Photobiology. 84:1381-1387 |
| ISSN: | 1751-1097 0031-8655 |
| DOI: | 10.1111/j.1751-1097.2008.00458.x |
| Popis: | Optical pump-probe spectroscopy in the nanosecond-microsecond timescale has been used to study the electron transfer reactions taking place within the Photosystem I reaction center of intact Chlamydomonas reinhardtii cells. The biphasic kinetics of phylloquinone (PhQ) reoxidation were investigated in double mutants that combine a mutation (PsaA-Y696F) near the primary acceptor chlorophyll, ec3A, with those near PhQA (PsaA-S692A, PsaA-W697F). The PsaA-S692A and PsaA-W697F mutations selectively lengthened the 200 ns lifetime component observed in the wild-type (WT). The reverse similar 20 ns component was unaltered in the single mutant, both in terms of lifetime and relative amplitude. However, both double mutants possessed a reverse similar 20 ns component (PhQB(-) reoxidation) with increased amplitude compared with the WT and the individual PhQA mutants. The component assigned to PhQA(-) reoxidation was slowed, like the individual PhQA mutants, and of lower amplitude, as observed in the single ec3A mutant. Hence, the effects of these mutations are almost entirely additive, providing strong support for the previously proposed bidirectional electron transfer model, which attributes the reverse similar 20 and reverse similar 200 ns phases to reoxidation of PhQB or PhQA, respectively. Moreover, in all the mutants investigated, it was also possible to observe an intermediate (approximately 180 ns) component, as previously reported for mutants of the PhQ(A) binding pocket (Biochim. Biophys. Acta [2006] 1757, 1529-1538), which we have tentatively attributed to forward electron transfer between the iron-sulfur clusters FX and FA/B. |
| Databáze: | OpenAIRE |
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