Nitrate reductase in Escherichia coli K-12: involvement of chlC, chlE, and chlG loci

Abstract

The properties of E. coli mutants which are defective with respect to nitrate reductase activity were examined. ChlE::Mu cts and chlG::Mu cts mutants were all chlorate resistant, and the strains that were examined all synthesized nitrate reductase apoenzyme. The chlE and chlG loci, like the chlA, chlB and chlD loci, are involved in the synthesis or insertion of Mo cofactor. At least 4 distinct phenotypic classes of chlC::Tn10 mutants, all of which were fully or partially sensitive to chlorate, were identified. Two of these classes may represent lesions in the structural genes for nitrate reductase subunits A and C. Two other classes may be altered in the regulation of the expression of nitrate reductase or other anaerobic enzymes. The mnemonic nar is proposed for naming individual genes within the chlC locus.