SUBSTITUTION OF AN ALANINE RESIDUE FOR GLYCINE-146 IN TMP KINASE FROMESCHERICHIA-COLI IS RESPONSIBLE FOR BACTERIAL HYPERSENSITIVITY TO BROMODEOXYURIDINE

The wild-type TMP kinases from Escherichia coli and from a strain hype rsensitive to 5-bromo-2'-deoxyuridine were characterized comparatively . The mutation at codon 146 causes the substitution of an alanine resi due for glycine in the enzyme, which is accompanied by changes in the relative affinities for 5-Br-UMP and TMP compared to those of the wild -type TMP kinase. Plasmids carrying the wild-type tmk gene from Escher ichia coli or Bacillus subtilis, but not the defective tmk gene, resto red the resistance to bromodeoxyuridine of an E. coli mutant strain.