The irreversible inactivation of ribonucleotide reductase from Escherichia coli by superoxide radicals.
The expression of superoxide dismutase in all aerobic living organisms supports the concept that superoxide radicals are toxic species. However, because of the limited chemical reactivity of superoxide, the mechanisms of this toxicity are still uncertain. Protein R2, the small component of ribonucleotide reductase, a key enzyme for DNA synthesis, is shown here to be irreversibly inactivated during incubation with an enzymatic generator of superoxide radicals, at neutral pH. During inactivation the essential tyrosyl radical of protein R2 is irreversibly destroyed. Full protection is afforded by superoxide dismutase. It is proposed that coupling between superoxide radicals and the radical protein R2 generates oxidized forms of tyrosine, tyrosine peroxide and 3,4-dihydroxyphenylalanine.
Gaudu
P
P
Laboratoire d' Etudes Dynamiques et Structurales de la Sélectivé, UMR CNRS 5616, Université Joseph Fourier, Grenoble, France.
Nivière
V
V
Pétillot
Y
Y
Kauppi
B
B
Fontecave
M
M
D004926:Escherichia coli / Q000201:enzymology*; D005609:Free Radicals; D010084:Oxidation-Reduction; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*; D013481:Superoxides / Q000494:pharmacology*; D014443:Tyrosine
D005609:Free Radicals; D013481:Superoxides; D014443:Tyrosine; D012264:Ribonucleotide Reductases