This is the C-terminal domain of NADH rubredoxin oxidoreductase present in Clostridium acetobutylicum. The majority of obligatory anaerobes detoxify micro-aerobic environments by consuming O2 via H2O-forming NADH oxidase. This enzyme offers an alternate reaction pathway for scavenging of O2 and reactive oxygen species, wherein the reducing equivalent is obtained from NADH [1].

1: Crystal structure of NADH:rubredoxin oxidoreductase from Clostridium acetobutylicum: a key component of the dioxygen scavenging system in obligatory anaerobes. Nishikawa K, Shomura Y, Kawasaki S, Niimura Y, Higuchi Y; Proteins. 2010;78:1066-1070. PMID:20017214