Transient thiyl radicals in yeast copper(I) thionein.
In an EPR study employing yeast copper(I) thionein, GSH and Cu-GSH it was shown that thiyl radicals could be successfully generated from the thiolate sulfur via oxidation by photochemically formed superoxide at 77 K. The g-value was 2.036. Essentially no EPR detectable copper(II) was monitored under the experimental conditions, indicating that the oxidation reduction process is restricted to the thiolate sulfur. The Cu(I)-thiolate chromophores remained fully intact as deduced from chiroptical and luminescence measurements. Thus, copper thionein is supposed to be actively involved in the scavenging of oxygen free radicals by a reversible thiolate oxidation reduction cycle. The coordinated Cu(I) seems to serve as a prominent candidate to stabilize the transiently formed thiyl radical.
Deters
D
D
Inorganic Biochemistry Department, Eberhard Karls University of Tübingen, Germany.
Hartmann
H J
HJ
Weser
U
U
D002352:Carrier Proteins; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D008668:Metallothionein / Q000737:chemistry*; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000737:chemistry*
C500769:CUP1-1 protein, S cerevisiae; D002352:Carrier Proteins; D005609:Free Radicals; C007121:copper thionein; D008668:Metallothionein