N-terminal sub-domain of the Rel homology domain (RHD) of nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-kappa B)
Proteins containing the Rel homology domain (RHD) are metazoan transcription factors. The RHD is composed of two structural sub-domains; this model characterizes the N-terminal RHD sub-domain of the NF-kappa B1 and B2 families of transcription factors, also referred to as class I members of the NF-kappa B family. In class I NF-kappa Bs, the RHD domain co-occurs with C-terminal ankyrin repeats. Family members include NF-kappa B1 and NF-kappa B2. NF-kappa B1 is commonly referred to as p105 or p50 (proteolytically processed form), while NF-kappa B2 is called p100 or p52 (proteolytically processed form). NF-kappa B proteins are part of a protein complex that acts as a transcription factor, which is responsible for regulating a host of cellular responses to a variety of stimuli. This complex tightly regulates the expression of a large number of genes, and is involved in processes such as adaptive and innate immunity, stress response, inflammation, cell adhesion, proliferation and apoptosis. The cytosolic NF-kappa B complex is activated via phosphorylation of the ankyrin-repeat containing inhibitory protein I-kappa B, which dissociates from the complex and exposes the nuclear localization signal of the heterodimer (NF-kappa B and REL). p105 and p100 may also act as I-kappa Bs due to their C-terminal ankyrin repeats.