Involved in the assembly of mitochondrial NADH:ubiquinone oxidoreductase complex (complex I) (PubMed:18179882, PubMed:28853723). May be involved in cell proliferation and survival of hormone-dependent tumor cells. May be a regulator of breast tumor cell invasion. Binds calmodulin. Interacts with NDUFAF3. (Microbial infection) Interacts with the vesicular stomatitis virus matrix protein/M; the interaction inhibits viral propagation. Expression is low in quiescent cells and is induced in exponentially proliferating cultures. Expression is also induced when prolactin is added to stationary cells. Induced by dietary differentiating agents such as butyrate and retinoic acid. Phosphorylated on serine. Prolactin stimulate serine phosphorylation (By similarity). The disease is caused by variants affecting the gene represented in this entry. Belongs to the NDUFAF4 family.