IκB kinase

Overview
The IκB kinase (IKK) enzyme complex is part of the upstream NF-κB signal transduction cascade. The IκBα (inhibitor of kappa B) protein inactivates the NF-κB transcription factor by masking the nuclear localization signals (NLS) of NF-κB proteins and keep them sequestered in an inactive state in the cytoplasm. IKK specifically phosphorylates the inhibitory IκBα protein. This phosphorylation results in the dissociation of IκBα from NF-κB and thereby activates NF-κB.

Structure
The IκB kinase complex is comprised of three subunits each encoded by a separate gene: The α- and β-subunits together are catalytically active whereas the γ-subunit serves a regulatory function.
 * IKKα (also known as IKK1)
 * IKKβ (also known as IKK2)
 * IKKγ (also known as NEMO)