Isolation, Characterization and Complementation Analysis of nir B Mutants of Escherichia coli Deficient Only in NADH-dependent Nitrite Reductase Activity

Abstract

Summary: Mutants have been isolated which lack NADH-dependent nitrite reductase activity but retain NADPH-dependent sulphite reductase and formate hydrogenlyase activities. These NirB–strains synthesize cytochrome c₅₅₂ and grow normally on anaerobic glyeerol—fumarate plates. The defects map in a gene, nir B, which is extremely close to cysG, the gene order being crp, nirB, cysG, aroB. Complementation studies established that nirB⁺ and cysG⁺ can be expressed independently. The data strongly suggest that nirB is the structural gene for the 88 kDal NADH-dependent nitrite oxidoreductase apoprotein (EC 1.6.6.4).