Formate is the hydrogen donor for the anaerobic ribonucleotide reductase from Escherichia coli.
During anaerobic growth Escherichia coli uses a specific ribonucleoside-triphosphate reductase (class III enzyme) for the production of deoxyribonucleoside triphosphates. In its active form, the enzyme contains an iron-sulfur center and an oxygen-sensitive glycyl radical (Gly-681). The radical is generated in the inactive protein from S-adenosylmethionine by an auxiliary enzyme system present in E. coli. By modification of the previous purification procedure, we now prepared a glycyl radical-containing reductase, active in the absence of the auxiliary reducing enzyme system. This reductase uses formate as hydrogen donor in the reaction. During catalysis, formate is stoichiometrically oxidized to CO2, and isotope from [3H]formate appears in water. Thus E. coli uses completely different hydrogen donors for the reduction of ribonucleotides during anaerobic and aerobic growth. The aerobic class I reductase employs redox-active thiols from thioredoxin or glutaredoxin to this purpose. The present results strengthen speculations that class III enzymes arose early during the evolution of DNA.
Mulliez
E
E
Laboratoire d'Etudes Dynamiques et Structurales de la Sélectivité, Centre National de la Recherche Scientifique 332, Université Joseph Fourier, Grenoble, France.
Ollagnier
S
S
Fontecave
M
M
Eliasson
R
R
Reichard
P
P
D000693:Anaerobiosis; D002245:Carbon Dioxide / Q000378:metabolism; D003570:Cytidine Triphosphate / Q000378:metabolism; D003845:Deoxycytosine Nucleotides / Q000096:biosynthesis; D004926:Escherichia coli / Q000201:enzymology*; D005561:Formates / Q000378:metabolism*; D005609:Free Radicals; D005998:Glycine / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D012264:Ribonucleotide Reductases / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
D003845:Deoxycytosine Nucleotides; D005561:Formates; D005609:Free Radicals; D007506:Iron-Sulfur Proteins; C030544:formic acid; D002245:Carbon Dioxide; C024107:2'-deoxycytidine 5'-triphosphate; D003570:Cytidine Triphosphate; D012264:Ribonucleotide Reductases; D005998:Glycine