The phosphorylation and ubiquitination of IkB kinase complex is mediated by two distinct pathways, either the classical or alternative pathway. In the classical NF-kB signaling pathway, the activated IKK complex, predominantly acting through IKK beta in an IKK gamma-dependent manner, catalyzes the phosphorylation of IkBs (at sites corresponding to Ser32 and Ser36 of human IkB-alpha or Ser19 and Ser22 of human IkB-beta), polyubiquitination (at sites corresponding to Lys21 and Lys22 of human IkB-alpha) and subsequent degradation by the 26S proteasome. The K-48 ubiquitination is mediated by the E2 ubiquitin ligases (or SCFs) formed by three subunits: Skp1, Cul A (Cdc53), and one of many F-box proteins.
Chicken IkB-alpha shows 71% identity to the human IkB alpha kinase. Multiple sequence alignment of the human and chicken IKB-alpha showed that chicken Ser36 and Ser40 correspond to human Ser32 and Ser 36 mentioned above.
There is insufficient data for chicken IkB beta to make a comparison with other species.