The Rel homology domain (RHD) is found in a family of eukaryotic transcription factors, which includes NF-kappaB, Dorsal, Relish, NFAT, among others. The RHD is composed of two structural domains: the N-terminal DNA binding domain that is similar to that found in P53, the C-terminal domain has an immunoglobulin-like fold (See ) that functions as a dimerisation domain. This entry represents the N-terminal DNA binding domain []. Some of these transcription factors appear to form multi-protein DNA-bound complexes []. Phosphorylation of the RHD appears to play a role in the regulation of some of these transcription factors, acting to modulate the expression of their target genes []. The RHD is composed of two immunoglobulin-like β-barrel subdomains that grip the DNA in the major groove. The N-terminal specificity domain resembles the core domain of the p53 transcription factor, and contains a recognition loop that interacts with DNA bases; the C-terminal dimerisation domain contains the site for interaction with I-kappaB [].
The Rel homology domain (RHD) is found in a family of eukaryotic transcription factors, which includes NF-kappaB, Dorsal, Relish, NFAT, among others. The RHD is composed of two structural domains: the N-terminal DNA binding domain that is similar to that found in P53, the C-terminal domain has an immunoglobulin-like fold (See ) that functions as a dimerisation domain. This entry represents the N-terminal DNA binding domain superfamily []. Some of these transcription factors appear to form multi-protein DNA-bound complexes []. Phosphorylation of the RHD appears to play a role in the regulation of some of these transcription factors, acting to modulate the expression of their target genes []. The RHD is composed of two immunoglobulin-like β-barrel subdomains that grip the DNA in the major groove. The N-terminal specificity domain resembles the core domain of the p53 transcription factor, and contains a recognition loop that interacts with DNA bases; the C-terminal dimerisation domain contains the site for interaction with I-kappaB [].
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) [, ]. c-Rel plays an important role in B cell proliferation and survival [].Proteins containing the Rel homology domain (RHD) are metazoan transcription factors. The RHD is composed of two structural sub-domains. This entry represents the N-terminal RHD sub-domain of the c-Rel family of transcription factors, categorized as a class II member of the NF-kappa B family. In class II NF-kappa Bs, the RHD domain co-occurs with a C-terminal transactivation domain (TAD) [, ].
Proteins in this group are responsible for the molecular basis of the blood group antigens, surface markers on the outside of the red blood cell membrane. Most of these markers are proteins, but some are carbohydrates attached to lipids or proteins [Reid M.E., Lomas-Francis C. The Blood Group Antigen Facts Book Academic Press, London / San Diego, (1997)]. The RH(CE) polypeptide (Rhesus C/E antigens) and RH(D) polypeptide (Rhesus D antigen) belong to the Rh blood group system and are associated with antigens that include C/c, E/e, D, f, C(e), C(w), C(x), V, E(w), G, Tar, VS, D(w), cE, amongst others.The Rh (Rhesus) blood group system is important in clinical medicine by virtue of being involved in haemolytic disease of the newborn, transfusion reactions, autoimmune haemolytic anaemias, and haemolytic reactions of non-immune origin []. The RH locus from RH(D)-positive donors contains 2 homologous structural genes, one of which encodes the D protein that carries the major antigen of the Rh system. Hydropathy analysis of the RhD gene product reveals 13 hydrophobic domains, all of which have been assumed to be transmembrane (TM) [].The proteins in this entry are related to ammonium transport [, ].
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 proteindimerisation, 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 modulatingthe 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 bindingaffinity 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) [, ].
