Catalyzes the reduction of nitrite to nitric oxide (NO), probably with azurin as electron donor. Essential for growth and survival in oxygen-depleted environments. Can also provide protection against killing by normal human sera. Fe(III)-[cytochrome c] + H2O + nitric oxide = Fe(II)-[cytochrome c] + 2 H(+) + nitrite Binds 1 Cu(+) ion. Binds 1 Cu(2+) ion. Homotrimer. By anaerobic and microaerophilic conditions in the presence of nitrite. Regulated by the gonococcal fnr and NarP homologs. Palmitoylated. Undetected during aerobic growth. Belongs to the multicopper oxidase family.