The I-kB kinase complex (IKK) functions as a mediator of NF-kB activation in response to multiple stimuli by phosphorylating I-kB inhibitor proteins and causing their degradation. IKK contains two structurally related catalytic subunits termed IKKA and IKKB as well as a noncatalytic subunit called IKKG/NEMO. IKK is composed of a IKKG/NEMO homodimer bound together with either an IKKA/IKKB heterodimer or an IKKB homodimer. Although IKKG /NEMO itself does not have kinase activity, it is essential for NF-kB activation likely via a scaffold function that is required for IKK activity. Mutations in the X-linked gene encoding IKKG can interfere with NF-kB signaling and lead to immunodeficiency disease.Synonyms: FIP-3, FIP3, I-kappa-B kinase subunit gamma, IKK-gamma, IKKAP1, IKKG, IkB kinase subunit gamma, IkB kinase-associated protein 1, Inhibitor of nuclear factor kappa-B kinase subunit gamma, NF-kappa-B essential modifier, NF-kappa-B essential modulator