ISSN:
1432-1327
Keywords:
Key words Ascorbate oxidase
;
Blue copper protein
;
Flash-photolysis
;
Nitrite reductase
;
Site-directed mutagenesis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract A site-directed mutant of spinach plastocyanin, Pc(Tyr83-His), has been modified by covalent attachment of a photoactive [Ru(bpy)2(im)]2+ complex to the His83 residue. The residue is surface exposed and located about 10–12 Å from the copper ion at the entrance of a proposed natural electron transfer pathway from cytochrome f. Electron transfer within the Ru-Pc complex has been studied with time-resolved optical spectroscopy using two different approaches. In the first, the fully reduced [Cu(I), Ru(II)] protein was photoexcited and subsequently oxidized by an external quencher, forming the [Cu(I), Ru(III)] protein. This was followed by an electron transfer from reduced Cu(I) to Ru(III). In the second method, the initially oxidized Cu(II) ion acted as an internal quencher for excited Ru(II) and the photoinduced reduction of the Cu(II) ion was followed by a thermal recombination with the Ru(III) ion. The reoxidation of the Cu ion, which has an estimated driving force of 0.56 eV, occured with a rate constant k et = (9.5±1.0)×106 s–1, observed with both methods. The results suggest a strong electronic coupling (H DA〉0.3 cm–1) along the Ru-His(83)-Cys(84)-Cu pathway.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050072
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