This family is the gamma subunit of the nitrate reductase enzyme, the gamma subunit is a b-type cytochrome that receives electrons from the quinone pool. It then transfers these via the iron-sulfur clusters of the beta subunit to the molybdenum cofactor found in the alpha subunit. The nitrate reductase enzyme, EC:184.108.40.206 catalyzes the conversion of nitrite to nitrate via the reduction of an acceptor. The nitrate reductase enzyme is composed of three subunits. Nitrate is the most widely used alternative electron acceptor after oxygen.