Protein Domain : NF-kappa-B/Dorsal IPR000451

Type	Family
Description	The transcription factor NF-kB (Nuclear Factor-kappaB) was first identified as a DNA-binding protein specific for the 10-base pair kB site in the immunoglobulin k light-chain enhancer of B lymphocytes [ ], but has subsequently been found in many different cell types. NF-kB represents a group of structurally related proteins that share a 300 amino acid `Rel homology domain' (RHD) []: members include p50 (NF-kB1), p52 (NF-kB2), p65 (RelA), c-Rel, v-Rrel, RelB, and the Drosophila proteins Dorsal and Dif. These proteins exist as homo- and heterodimers that bind to kB sites in the enhancer regions of several target genes, most of which are involved in cellular defence mechanisms and differentiation.The RHD, which is located N-terminally, is responsible for protein dimerisation, DNA binding and nuclear localisation. The more variableC-terminal transactivation domain is found in RelA, RelB and c-Rel, but not in p50 or p52. Nevertheless, p50 and p52 play critical roles in modulating the specificity of NF-kB function. DNA binding requires the entire RHD, by contrast with other eukaryotic and prokaryotic transcription factors, where muchsmaller DNA-binding domains confer full specificity and binding affinity for the target []. The structure of the transcription factor NF-kB p50 homodimer bound to a palindromic kB site shows the RHD to fold into 2 distinct subdomains, similar to the β-sandwich structure of the immunoglobulins [].NF-kB is expressed in the cytoplasm of virtually all cell types, where its activity is controlled by a family of regulatory proteins, called inhibitors of NF-kB (IkB) [ , ].
Short Name	NFkB/Dor