title: Activation of the anaerobic ribonucleotide reductase from Escherichia coli by S-adenosylmethionine.
abstract: The anaerobic ribonucleoside triphosphate reductase from Escherichia coli reduces CTP to dCTP in the presence of a second protein, named dA1, and a Chelex-treated boiled extract of the bacteria, named RT. The reaction requires S-adenosylmethionine, NADPH, dithiothreitol, ATP, and Mg2+ and K+ ions. It occurs only under anaerobic conditions. We now show that the overall reaction occurs in two steps. The first is an activation of the reductase by dA1 and RT and requires S-adenosylmethionine, NADPH, dithiothreitol, and possibly K+ ions. In the second step, the activated reductase reduces CTP to dCTP with ATP acting as an allosteric effector. During activation, S-adenosylmethionine is cleaved reductively to methionine + 5'-deoxyadenosine. This step is inhibited strongly by S-adenosylhomocysteine and various chelators. The activation of the anaerobic reductase shows a considerable similarity to that of pyruvate formate-lyase (Knappe, J., Neugebauer, F. A., Blaschkowski, H. P., and Gänzler, M. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 1332-1335).
authors.affiliation: Department of Biochemistry, Karolinska Institutet, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Harder
authors.forename: R
authors.initials: R
authors.lastname: Eliasson
authors.forename: E
authors.initials: E
authors.lastname: Pontis
authors.forename: M D
authors.initials: MD
authors.lastname: Ballinger
authors.forename: P
authors.initials: P
authors.lastname: Reichard
mesh_terms: D000693:Anaerobiosis; D003570:Cytidine Triphosphate / Q000378:metabolism; D003839:Deoxyadenosines / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008954:Models, Biological; D010084:Oxidation-Reduction; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D012435:S-Adenosylhomocysteine / Q000494:pharmacology; D012436:S-Adenosylmethionine / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D003839:Deoxyadenosines; D003570:Cytidine Triphosphate; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D008715:Methionine; D012264:Ribonucleotide Reductases