A pulse radiolytic study on the reaction of hydroxyl and superoxide radicals with yeast Cu(I)-thionein.
In a pulse radiolytic study employing aqueous intact yeast copper(I)-thionein at pH 7 it was shown that both superoxide and hydroxyl radicals efficiently react with this Cu(I)- and thiolate-rich protein. The reaction constant of hydroxyl radicals with Cu(I)-thionein was determined by competition kinetics and was 2.2 x 10(11) M-1 s-1 at a rate close to a diffusion-controlled limit. The reaction of Cu(I)-thionein with superoxide was also successful and proceeded at a rate of 7.5 x 10(6) M-1 s-1. According to chiroptical and luminescence emission measurements minor oxidation of the copper(I)-thiolate oligonuclear binding centres was observed, leading to the release of some Cu(II). It is important to realise the dual reactivity of this yeast Cu(I)-thiolate protein in controlling copper transport and storage as well as its distinct role in the scavenging of free radicals.
Felix
K
K
Strahlenbiologisches Institut, Ludwig-Maximilians-Universität München, Germany.
Lengfelder
E
E
Hartmann
H J
HJ
Weser
U
U
D001665:Binding Sites; D002352:Carrier Proteins; D005609:Free Radicals; D005978:Glutathione / Q000378:metabolism; D017665:Hydroxyl Radical / Q000737:chemistry*; D008668:Metallothionein / Q000737:chemistry*; D008956:Models, Chemical; D009942:Organometallic Compounds / Q000737:chemistry; D011675:Pulse Radiolysis; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013481:Superoxides / Q000737:chemistry*
C500769:CUP1-1 protein, S cerevisiae; D002352:Carrier Proteins; D005609:Free Radicals; D009942:Organometallic Compounds; C007121:copper thionein; C048402:copper(I)-thiolate; D013481:Superoxides; D017665:Hydroxyl Radical; D008668:Metallothionein; D005978:Glutathione