This entry represents NADH dehydrogenase [ubiquinone] iron-sulfur protein 4, an accessory subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I), initially identified in Neurospora crassa as a 21 kDa protein [1,2]. It is believed that members of this family are not to be involved in catalysis.

1: Complementary DNA sequences of the 24 kDa and 21 kDa subunits of complex I from Neurospora. Azevedo JE, Duarte M, Belo JA, Werner S, Videira A; Biochim Biophys Acta 1994;1188:159-161. PMID:7947902

2: Remodeled respiration in ndufs4 with low phosphorylation efficiency suppresses Arabidopsis germination and growth and alters control of metabolism at night. Meyer EH, Tomaz T, Carroll AJ, Estavillo G, Delannoy E, Tanz SK, Small ID, Pogson BJ, Millar AH; Plant Physiol. 2009;151:603-619. PMID:19675153