InterPro domain: IPR010228

This entry describes the G subunit (one of 14 subunits, A to N) of the NADH-quinone oxidoreductase complex I which generally couples NADH and ubiquinone oxidation/reduction in bacteria and mammalian mitochondria while translocating protons, but may act on NADPH and/or plastoquinone in cyanobacteria and plant chloroplasts. This family does not contain related subunits from formate dehydrogenase complexes.

NADH:ubiquinone oxidoreductase (complex I) ( 7.1.1.2 ) is a respiratory-chain enzyme that catalyses the transfer of two electrons from NADH to ubiquinone in a reaction that is associated with proton translocation across the membrane (NADH + ubiquinone = NAD+ + ubiquinol) [ 1 ]. Complex I is a major source of reactive oxygen species (ROS) that are predominantly formed by electron transfer from FMNH(2). Complex I is found in bacteria, cyanobacteria (as a NADH-plastoquinone oxidoreductase), archaea [ 2 ], mitochondria, and in the hydrogenosome, a mitochondria-derived organelle. In general, the bacterial complex consists of 14 different subunits, while the mitochondrial complex contains homologues to these subunits in addition to approximately 31 additional proteins [ 3 ].

1. The NADH:ubiquinone oxidoreductase (complex I) of respiratory chains. Q. Rev. Biophys. 25, 253-324
2. The respiratory complex I of bacteria, archaea and eukarya and its module common with membrane-bound multisubunit hydrogenases. FEBS Lett. 479, 1-5
3. Assembly of the Escherichia coli NADH:ubiquinone oxidoreductase (complex I). Biochim. Biophys. Acta 1777, 735-9