Ubiquitinated TRAF6 recruits TAB2 and activates the TAB2-associated TAK1 kianse by promoting the autophosphorylation of TAK1. TAB2 contains an N-term pseudophosphatase domain, which is indispensable for TAK1 activation, and a C-term domain that binds to and activates TAK1. The activation of TAK1/TAB2 complex requires a ubiquitination reaction catalysed by E1, Ubc13/Uev1A (E2) and TRAF6 (E3). TAK1 undergoes autophosphorylation on residues T184 and T187 and gets activated. Activated TAK1 then phosphorylates and activates IKK beta.