Novel mutator mutants of E. coli nrdAB ribonucleotide reductase: insight into allosteric regulation and control of mutation rates

DNA Repair (Amst). 2012 May 1;11(5):480-7. doi: 10.1016/j.dnarep.2012.02.001. Epub 2012 Mar 13.


Ribonucleotide reductase (RNR) is the enzyme critically responsible for the production of the 5'-deoxynucleoside-triphosphates (dNTPs), the direct precursors for DNA synthesis. The dNTP levels are tightly controlled to permit high efficiency and fidelity of DNA synthesis. Much of this control occurs at the level of the RNR by feedback processes, but a detailed understanding of these mechanisms is still lacking. Using a genetic approach in the bacterium Escherichia coli, a paradigm for the class Ia RNRs, we isolated 23 novel RNR mutants displaying elevated mutation rates along with altered dNTP levels. The responsible amino-acid substitutions in RNR reside in three different regions: (i) the (d)ATP-binding activity domain, (ii) a novel region in the small subunit adjacent to the activity domain, and (iii) the dNTP-binding specificity site, several of which are associated with different dNTP pool alterations and different mutational outcomes. These mutants provide new insight into the precise mechanisms by which RNR is regulated and how dNTP pool disturbances resulting from defects in RNR can lead to increased mutation.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Allosteric Regulation / genetics
  • Deoxyribonucleosides / metabolism
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics*
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Gene Order
  • Models, Molecular
  • Mutant Proteins / genetics
  • Mutant Proteins / isolation & purification
  • Mutant Proteins / metabolism
  • Mutation
  • Mutation Rate*
  • Protein Conformation
  • Ribonucleoside Diphosphate Reductase / chemistry
  • Ribonucleoside Diphosphate Reductase / genetics
  • Ribonucleoside Diphosphate Reductase / metabolism*
  • Ribonucleotide Reductases / chemistry
  • Ribonucleotide Reductases / genetics
  • Ribonucleotide Reductases / metabolism*


  • Deoxyribonucleosides
  • Escherichia coli Proteins
  • Mutant Proteins
  • NrdB protein, E coli
  • Ribonucleotide Reductases
  • NrdA protein, E coli
  • Ribonucleoside Diphosphate Reductase