title: Comparison of the rep-38 and mmrA1 mutations of Escherichia coli.
abstract: The rep-38 and mmrA1 mutations are located very close to each other (approximately 85 min), and have been suggested to be allelic. To address this question we have compared the phenotypes of the mmrA1 and rep-38 mutants. Both the mmrA1 and rep-38 mutations blocked the enhanced killing and inhibition of postreplication repair by rich growth medium that occurs in UV-irradiated Escherichia coli K-12 uvrA cells, i.e., the mmrA1 and rep-38 strains did not show minimal medium recovery (MMR). However, phi X174 bacteriophage propagated well in mmrA1 strains, but not in rep-38 strains; a rep mutation sensitized a uvrA strain to UV irradiation, but a mmrA mutation did not. During chloramphenicol treatment, the rep-38 strain showed a larger amount of residual DNA synthesis than observed in the mmrA1 strain. The mmrA1 mutation appears to be a dominant mutation. This was determined by the failure of either plasmid pLC44-7 or episome F'KLF11, both of which carry the mmrA+ gene, to complement the Mmr- phenotype of a uvrA mmrA strain. Plasmid pLC44-7 is known to complement the rep-38 mutation, suggesting that rep-38 is a recessive mutation. Although certain of the phenotypes of the rep and mmrA mutants are similar, a number are quite different. These differences suggest that these two mutations are not allelic.
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics*; D010584:Bacteriophage phi X 174 / Q000235:genetics; D004265:DNA Helicases; D004261:DNA Replication; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects; D029968:Escherichia coli Proteins; D005838:Genotype; D007700:Kinetics; D009154:Mutation; D010641:Phenotype; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C506744:rep protein, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases