Mechanism of Action of Nalidixic Acid on Escherichia coli VI. Cell-free Studies

Abstract

The effects of nalidixic acid in vitro on deoxyribonucleic acid (DNA)- polymerase (deoxyribonucleosidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7), deoxyribonucleotide kinases (ATP: deoxymono- and diphosphate phosphotransferases), and deoxyribosyl transferase (nucleoside: purine deoxyribosyltransferase, EC 2.4.2.6) were examined employing partially purified and crude extracts of Escherichia coli ATCC 11229 and E. coli 15TAU. Nalidixic acid had no inhibitory effect on the DNA-polymerase of the wild-type strain E. coli ATCC 11229 at concentrations of 1.4 × 10 −3 to 2.8 × 10 −3 m . No inhibition of deoxyribonucleotide kinase activity was observed at concentrations of nalidixic acid ranging from 2 × 10 −3 to 8.6 × 10 −3 m . Nalidixic acid (0.43 × 10 −4 to 0.43 × 10 −3 m ) had no inhibitory effect on the deoxyribosyl transferase activity of crude extracts obtained from E. coli ATCC 11229 or E. coli 15TAU. Analytical CsCl density gradient centrifugation demonstrated that the DNA obtained after treatment of E. coli 15TAU with nalidixic acid was not cross-linked. These results suggest that the prevention of DNA synthesis in vivo by nalidixic acid is not attributable to inhibition of DNA polymerase, deoxyribonucleotide kinase, deoxyribosyl transferase, or to cross-linking of the DNA of treated cells.