3.D.4.2.2
Nitrous oxide reductase, NosZ, of 652 aas with one N-terminal TMS. The NosZ enzyme is the terminal reductase of anaerobic N₂O respiration.  Electrons derived from a donor substrate are transferred to NosZ by means of an electron transport chain (ETC) that conserves energy through proton motive force generation (Hein and Simon 2019). In both clade I and clade II NosZs, proton motive quinol oxidation by N₂O is thought to be catalyzed by the Q cycle mechanism of a membrane-bound Rieske/cytochrome bc complex (Hein and Simon 2019). Nitrous-oxide reductase is part of a bacterial respiratory system which is activated under anaerobic conditions in the presence of nitrate or nitrous oxide. NosZ is similar in sequence to cytochrome c oxidase component 2 only in the C-terminal 100 aa residues of both proteins which contains a pair of cysteyl residues.