Reconstitution of the Electron Transport System That Couples Formate Oxidation to Nitrogenase in Methylosinus trichosporium OB3b

Abstract

The electron transfer system that transports electrons from formap to nitrogenase was examined in extracts of the obligate methanotroph Methylosinus trichosporium OB3b. By supplementing a crude nitrogenase extract with NAD, formate dehydrogenase, NADH-ferredoxin reductase and FMN (an FDH cofactor), an electron transport system was established that coupled formate oxidation to nitrogendependent acetylene reduction. The ferredoxin dependence of this reaction was demonstrated by its severe inhibition by antibodies to ferredoxin. The reaction sequence is as follows : formate + formate debydrogenase NADH + NADH-ferredoxin reductase-+ ferredoxin + nitrogenase.