Electron transport to nitrogenase in Klebsiella pneumoniae.

Cell-free extracts of nifF and nifJ mutants of Klebsiella pneumoniae are unable to couple acetylene reduction (N2 fixation) by nitrogenase to the oxidation of organic metabolites. However, nifF and nifJ mutants can complement each other in vitro to establish the coupling. This indicates that the products of the nifF and nifJ genes constitute essential elements of the physiological electron pathway to nitrogenase. The electron-transfer-active product of the nifF gene, a flavoprotein, has been purified.