Restoration of reduced nicotinamide adenine dinucleotide phosphate-nitrate reductase activity of a Neurospora mutant by extracts of various chlorate-resistant mutants of Escherichia coli.

Acid-treated extracts of Escherichia coli were tested for their ability to restore reduced nicotinamide adenine dinucleotide phosphate-nitrate reductase activity to an extract of a Neurospora nit-1 mutant which produces a defective enzyme. With wild-type E. coli this complementation activity was more readily detected in the cytoplasmic fraction, although the nitrate reductase activity was found primarily in the particulate fraction. chlB mutants of E. coli appeared to have more complementation activity in the cytoplasm than was observed in the wild type, but no activity in the particulate fraction. The other chl mutants had little or no activity in either fraction. These results suggest that chlB mutants can produce a component or cofactor which is missing in the other mutants and in the Neurospora mutant, but cannot transfer it to the nitrate reductase enzyme.