RESUMO
cls and nov mutants have similar increased sensitivities to novobiocin and reduced levels of cardiolipin, both of which can be corrected by plasmid-borne copies of either wild-type gene. A comparison of the DNA sequences of both genes further verifies their identity.
Assuntos
Escherichia coli/genética , Genes Bacterianos/genética , Proteínas de Membrana , Novobiocina/farmacologia , Transferases (Outros Grupos de Fosfato Substituídos)/genética , Escherichia coli/enzimologia , Teste de Complementação Genética , Genótipo , Mutação , Fosfatidiletanolaminas/análise , Fosfatidilgliceróis/análiseRESUMO
In a previous study, we demonstrated the existence of a gene locus, nov, which affects resistance of Escherichia coli K-12 to the gyrase inhibitor novobiocin and, to a lesser degree, coumermycin (J. Rakonjac, M. Milic, D. Ajdic, D. Santos, R. Ivanisevic, and D. J. Savic, Mol. Microbiol. 6:1547-1553, 1992). In the present study, sequencing of the nov gene locus revealed one open reading frame that encodes a protein of 54,574 Da, a value. found to be in correspondence with the size of the Nov protein identified in an in vitro translation system. We also located the 5' end of the nov transcript 8 bp downstream from a classical sigma70 promoter. Transcription of the gene is in the counterclockwise direction on the E. coli chromosome. Transposon mutagenesis of nov followed by complementation analyses and replacement of chromosomal alleles with mutated nov confirmed our previous assumption that the nov gene exists in two allelic forms and that the Novr gene is an active allele while the Novs gene is an inactive form. After comparing nucleotide sequences flanking the nov gene with existing data, we conclude that the gene order in this region of the E. coli K-12 map is att phi 80-open reading frame of unknown function-kch (potassium channel protein)-nov-opp. Finally, the possible identity of the nov gene with cls, the gene that codes for cardiolipin synthase, is also discussed.
Assuntos
Resistência Microbiana a Medicamentos/genética , Escherichia coli/efeitos dos fármacos , Genes Bacterianos , Novobiocina/farmacologia , Inibidores da Topoisomerase II , Transcrição Gênica , Alelos , Sequência de Bases , Análise Mutacional de DNA , Elementos de DNA Transponíveis , Escherichia coli/genética , Teste de Complementação Genética , Dados de Sequência MolecularRESUMO
We have identified a new gene locus (nov) affecting the resistance of Escherichia coli K-12 to novobiocin. The gene also affects, although to a lesser extent, tolerance to another gyrase inhibitor coumermycin. Transductional and complementation analysis show that nov is located between att phi 80 and the osmZ (hns) genes at minute 27 of the E. coli K-12 genetic map. In standard laboratory strains of E. coli K-12 nov exists at least in two allelic forms.
