The NarG-like domain was originally characterised in the molybdo-bis(molybdopterin guanine dinucleotide) (Mo-bisMGD) cofactor-binding subunit NarG from nitrate reductase subunit. It is also found in homologous subunits from other oxidorectuases such as the coenzymeB--coenzymeM heterodisulphide reductase subunit E. Structurally this domain is composed of four alpha-beta subdomains that are organised around the catalytic centre of the enzyme complex [<cite idref="PUB00017049"/>]. Subdomains II and III are organised around the Mo-bisMGD cofactor.