Photo-accumulation of the P+ QB − radical pair state in purple bacterial reaction centres that lack the QA ubiquinone
| Autor: | Matthew G. Goodwin, Marion C. Wakeham, Craig McKibbin, Michael R. Jones |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Free Radicals
Photochemistry Ubiquinone Stereochemistry Photosynthetic Reaction Center Complex Proteins Biophysics Protonation Electron donor Rhodobacter sphaeroides Biochemistry Reaction centre Electron transfer Inactive branch chemistry.chemical_compound Structural Biology Genetics Photosynthesis Molecular Biology Spectroscopy Alanine biology Chemistry Stigmatellin Cell Biology biology.organism_classification Quinone Mutagenesis Yield (chemistry) Potentiometry |
| Zdroj: | FEBS Letters. 540:234-240 |
| ISSN: | 0014-5793 |
| DOI: | 10.1016/s0014-5793(03)00270-9 |
| Popis: | Photo-excitation of membrane-bound Rhodobacter sphaeroides reaction centres containing the mutation Ala M260 to Trp (AM260W) resulted in the accumulation of a radical pair state involving the photo-oxidised primary electron donor (P). This state had a lifetime of hundreds of milliseconds and its formation was inhibited by stigmatellin. The absence of the Q(A) ubiquinone in the AM260W reaction centre suggests that this long-lived radical pair state is P(+)Q(B)(-), although the exact reduction/protonation state of the Q(B) quinone remains to be confirmed. The blockage of active branch (A-branch) electron transfer by the AM260W mutation implies that this P(+)Q(B)(-) state is formed by electron transfer along the so-called inactive branch (B-branch) of reaction centre cofactors. We discuss how further mutations may affect the yield of the P(+)Q(B)(-) state, including a double alanine mutation (EL212A/DL213A) that probably has a direct effect on the efficiency of the low yield electron transfer step from the anion of the B-branch bacteriopheophytin (H(B)(-)) to the Q(B) ubiquinone. |
| Databáze: | OpenAIRE |
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