Effects of Inhibitors on the Activity of the Cytochrome b6f Complex: Evidence for the Existence of Two Binding Pockets in the Lumenal Site
| Autor: | Giovanni Finazzi, Romina Paola Barbagallo, Giorgio Forti |
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| Rok vydání: | 1999 |
| Předmět: | |
| Zdroj: | Biochemistry. 38:12814-12821 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi990424+ |
| Popis: | The effects of two inhibitors of electron transfer in the cytochrome b6f complex have been studied in whole cells of Chlamydomonas reinhardtii. DNP-INT affected equally the two steps of the concerted oxidation of plastoquinol at the Qo site; it decreased the rates of both cytochrome f reduction and cytochrome b6 turnover, without affecting the amplitude of their redox signals. On the contrary, DBMIB inhibited only the rate of cytochrome f reduction while reducing, at the same time, the amplitude of cytochrome b6 signals. The accessibility of DNP-INT to the Qo site was unaffected by preillumination, while that of DBMIB was greatly enhanced, even after a single turnover of the cytochrome b6f complex. Similar results were obtained with a mutant strain (FUD2) where the Qo site has an affinity for plastoquinol that is diminished by a factor of ∼50 [Finazzi, G., et al. (1997) Biochemistry 36, 2867−2874]. However, the binding of the two inhibitors was differentially influenced by the mutation: a factor of ∼250 ... |
| Databáze: | OpenAIRE |
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