Fig. 1

The mammalian NF-κB and IκB families. The five members of the NF-κB family are schematically shown, with the major domains highlighted and the alternative names indicated in parenthes. The rel-homology domain (RHD) mediates DNA-binding and dimerization functions, the transactivation domain (TD) is required for transcriptional activation of target genes, whereas the leucine zipper (LZ) motif is also involved in target gene transactivation. The IκB family includes the p50 precursor protein p105, the p52 precursor protein p100, IκBα, IκBβ, IκBε, and several atyipical IκB members that are not shown in the figure. A hallmark of IκB members if the presence of ankyrin repeats that are required for inhibition of NF-κB. The death domain (DD) of p105 and p100 is also important for their IκB-like functions. The PEST (proline, glutamine, serine, and threonine)-like sequence of IκBα and IκBβ mediates protein turnover. RHD rel-homology domain, TD transactivation domain, LZ leucine zipper, DD death domain, PEST proline, glutamine, serine, and threonine