This entry represents the N-terminal domain of TfoX from Haemophilus influenzae. TfoX Positively regulates genes required for DNA transformation (late competence-specific genes) in association with CRP []. This domain can also be found in Sxy from Escherichia coli. Sxy induces low levels of natural DNA uptake by inducing transcription of the competence genes (the CRP-S regulon) required for DNA transformation [, ].
The Crp-type HTH domain is a DNA-binding, winged helix-turn-helix (wHTH) domain of about 70-75 amino acids present in transcription regulators of the crp-fnr family, involved in the control of virulence factors, enzymes of aromatic ring degradation, nitrogen fixation, photosynthesis, and varioustypes of respiration. The Crp-Fnr family is named after the first members identified in Escherichia coli: the well characterised cyclic AMP receptor protein CRP or CAP (catabolite activator protein) and the fumarate and nitrate reductase regulator Fnr. Crp-type HTH domain proteins occur in most bacteria and in chloroplasts of red algae. The DNA-binding HTH domain is located in the C-terminal part; the N-terminal part of the proteins of the Crp-Fnr family contains a nucleotide-binding domain and a dimerization/linker helix occurs in between. The Crp-Fnr regulators predominantly act as transcription activators, but can also be important repressors, and respond to diverse intracellular and exogenous signals, such as cAMP, anoxia, redox state, oxidative and nitrosative stress, carbon monoxide, nitric oxide or temperature [, ].
Pentraxin-related protein PTX3 is a long pentraxin that provides defence against infectious agents and plays several functions in tissue repair and regulation of cancer-related inflammation [].Pentraxins are a family of evolutionarily conserved molecules with regulatory role in inflammation. They share the "pentraxin signature"(His-x-Cys-x-Ser/Thr-Trp-x-Ser, where x is any amino acid) and can be divided into a short and a long arm based on their structural organization. Short pentraxins, feature a peculiar quaternary structure with five or ten identical protomer subunits arranged into symmetric pentamers, such as CRP and SAP, are secreted proteins produced by hepatocytes in response to IL-6. Long pentraxins, on the other end, display an unrelated amino-terminal region coupled to a C-terminal pentraxin domain. PTX3 is the prototype of the long pentraxin subfamily produced by myeloid and stromal cells, but not by hepatocytes, in response to primary pro-inflammatory cytokines or microbial moieties [].
This entry represents Pentaxins and its related proteins such as CRP (C-reactive protein) and SAP (serum amyloid P component protein) []. This entry also includes adhesion G-protein coupled receptors D2 and G6 from humans.Pentraxins (or pentaxins) [, ]are a family of proteins which show, under electron microscopy, a discoid arrangement of five noncovalently bound subunits. Proteins of the pentraxin family are involved in acute immunological responses []. Three of the principal members of the pentraxin family are serum proteins and Ca2 dependent: namely, C-reactive protein (CRP) [], serum amyloid P component protein (SAP) [], and female protein (FP) []. CRP binds to ligands containing phosphocholine, SAP binds to amyloid fibrils, DNA, chromatin, fibronectin, C4-binding proteins and glycosaminoglycans.CRP is expressed during acute phase response to tissue injury or inflammation in mammals. The protein resembles antibody and performs several functions associated with host defence: it promotes agglutination, bacterial capsular swelling and phagocytosis, and activates the classical complement pathway through its calcium-dependent binding to phosphocholine. CRPs have also been sequenced in an invertebrate, Limulus polyphemus (Atlantic horseshoe crab), where they are a normal constituent of the hemolymph [].SAP is a vertebrate protein that is a precursor of amyloid component P. It is found in all types of amyloid deposits, in glomerular basement menbrane and in elastic fibres in blood vessels. SAP binds to various lipoprotein ligands in a calcium-dependent manner, and it has been suggested that, in mammals, this may have important implications in atherosclerosis and amyloidosis [].FP is a SAP homologue found in Mesocricetus auratus (golden hamster). The concentration of this plasma protein is altered by sex steroids and stimuli that elicit an acute phase response."Long"pentraxins have N-terminal extensions to the common pentraxin domain []; one group, the neuronal pentraxins, may be involved in synapse formation and remodeling, and they may also be able to form heteromultimers []. Pentraxin proteins expressed in the nervous system are neural pentraxin I (NPI) and II (NPII) []. NPI and NPII are homologous and can exist within one species. It is suggested that both proteins mediate the uptake of synaptic macromolecules and play a role in synaptic plasticity. Apexin, a sperm acrosomal protein, is a homologue of NPII found in Cavia porcellus (Guinea pig) [].PTX3 is a long pentraxin that provides defence against infectious agents and plays several functions in tissue repair and regulation of cancer-related inflammation [].
The crp-type HTH domain is a DNA-binding, winged helix-turn-helix (wHTH) domain of about 70-75 amino acids present in transcription regulators of the crp-fnr family, involved in the control of virulence factors, enzymes of aromatic ring degradation, nitrogen fixation, photosynthesis, and various types of respiration. The crp-fnr family is named after the first members identified in Escherichia coli: the well characterised cyclic AMP receptor protein CRP or CAP (catabolite activator protein) and the fumarate and nitrate reductase regulator Fnr. crp-type HTH domain proteins occur in most bacteria and in chloroplasts of red algae. The DNA-binding HTH domain is located in the C-terminal part; the N-terminal part of the proteins of the crp-fnr family contains a nucleotide-binding domain and a dimerisation/linker helix occurs in between. The crp-fnr regulators predominantly act as transcription activators, but can also be important repressors, and respond to diverse intracellular and exogenous signals, such as cAMP, anoxia, redox state, oxidative and nitrosative stress, carbon monoxide, nitric oxide or temperature []. The structure of the crp-type DNA-binding domain shows that the helices (H) forming the helix-turn-helix motif (H2-H3) are flanked by two β-hairpin (B) wings, in the topology H1-B1-B2-H2-H3-B3-B4. Helix 3 is termed the recognition helix, as in most wHTHs it binds the DNA major groove [, , ]. Some proteins known to contain a Crp-type HTH domain: E. coli crp (also known as cAMP receptor), a protein that complexes with cAMP and regulates the transcription of several catabolite-sensitive operons. E. coli fnr, a protein that activates genes for proteins involved in a variety of anaerobic electron transport systems. Rhizobium leguminosarum fnrN, a transcription regulator of nitrogen fixation. Rhodobacter sphaeroides (Rhodopseudomonas sphaeroides) fnrL, a transcription activator of genes for heme biosynthesis, bacteriochlorophyll synthesis and the light-harvesting complex LHII. Rhizobiacae fixK, a protein that regulates nitrogen fixation genes, both positively and negatively. Lactobacillus casei fnr-like protein flp, a putative regulatory protein linked to the trpDCFBA operon. Cyanobacteria ntcA, a regulator of the expression of genes subject to nitrogen control. Xanthomonas campestris clp, a protein involved in the regulation of phytopathogenicity. Clp controls the production of extracellular enzymes, xanthan gum and pigment, either positively or negatively.
Pentaxins (or pentraxins) [, ]are a family of proteins which show, underelectron microscopy, a discoid arrangement of five noncovalently boundsubunits. Proteins known to belong to this family are:C-reactive protein (CRP), a protein which, in mammals,is expressed duringacute phase response to tissue injury or inflammation. CRP displays severalfunctions associated with host defense: it promotes agglutination,bacterial capsular swelling, phagocytosis and complement fixation throughits calcium-dependent binding to phosphorylcholine. CRPs have also beensequenced in an invertebrate, the Atlantic horseshoe crab, where they are anormal constituent of the hemolymph.Serum Amyloid P-component (SAP), a precursor of amyloid component P whichis found in basement membrane and is associated with amyloid deposits.Hamster female protein (FP), a plasma protein whose concentration isaltered by sex steroids and stimuli that elicit an acute phase response.A number of proteins, whose function is not yet clear, contain a C-terminalpentaxin-like domain. These proteins are:Human PTX3 (or TSG-14). PTX3 is a cytokine-induced protein.Guinea pig apexin [], a sperm acrosomal protein. Apexin seems to be theortholog of human neuronal pentraxin II (gene NPTX2) [].Rat neuronal pentaxin I [].The sequences of the different members of this family are quite conserved. This entry represents a six residue pattern which includes a cysteineknown to be involved in a disulfide bridge in CRPs and SAP.
