Home About us Contact
|
Home About us Contact | ||
|
|
||
Domain Homologous (domain + homologous)
Selected AbstractsToll-like receptor 9 binds single-stranded CpG-DNA in a sequence- and pH-dependent mannerEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2004Mark Rutz Abstract Toll-like receptors (TLR) recognize bacterial and viral components, but direct interaction of receptor and ligand is unclear. Here, we demonstrate that TLR9 binds directly and sequence-specifically to single-stranded unmethylated CpG-DNA containing a phosphodiester backbone. TLR9-CpG-DNA interaction occurs at the acidic pH (6.5,5.0) found in endosomes and lysosomes. By sequence comparison we identified a potential CpG-DNA binding domain homologous to that described for methyl-CpG-DNA binding proteins. Amino acid substitutions in this region abrogated CpG-DNA binding and led to loss of NF-,B activation. Furthermore, chloroquine and quinacrine, therapeutic agents for autoimmune diseases like rheumatoid arthritis and systemic lupus erythematosus, directly blocked TLR9-CpG-DNA interaction but not TLR2-Pam3Cys binding. Our results demonstrate direct binding of TLR9 to CpG-DNA and suggest that the therapeutic activity of chloroquine and quinacrine in autoimmune diseases may be due to its activity as a TLR9 antagonist and inhibitor of endosomal acidification. [source] Discoidin domain receptor 1 mediates collagen-induced inflammatory activation of microglia in cultureJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2008Min-Chul Seo Abstract Discoidin domain receptor 1 (DDR1) is a nonintegrin collagen receptor tyrosine kinase with an extracellular domain homologous to discoidin 1 of a soil-living amoeba Dictyostelium discoideum. We have previously demonstrated that DDR1 mediates collagen-induced nitric oxide production in J774A.1 murine macrophages. Because collagen is one of the main components of extracellular matrix in the central nervous system, we hypothesized that collagen also induces inflammatory activation of brain microglia, and DDR1 may mediate collagen-induced microglial activation. Using BV-2 mouse microglial cells and mouse primary microglial cultures, we have demonstrated that (1) collagen induces inflammatory activation of microglia as evidenced by production of nitric oxide, expression of inducible nitric oxide synthase, COX-2, CD40, and matrix metalloproteinase,9; (2) DDR1 is expressed in microglia and is phosphorylated by collagen treatment; and (3) collagen-induced microglial activation is abrogated by DDR1 blockade but not by integrin neutralization. We have further shown that p38 MAPK, c-Jun N-terminal kinase, and nuclear factor,kappa B are involved in the collagen-DDR1-induced microglial activation. Our results suggest that collagen can induce inflammatory activation of brain microglia and that DDR1 mediates this effect of collagen in an integrin-independent manner. © 2007 Wiley-Liss, Inc. [source] New functions for the ancient globin family: bacterial responses to nitric oxide and nitrosative stressMOLECULAR MICROBIOLOGY, Issue 4 2000MicroReview Globin-like oxygen-binding proteins occur in bacteria, yeasts and other fungi, and protozoa. The simplest contain protohaem as sole prosthetic group, but show considerable variation in their similarity to the classical animal globins and plant globins. Flavohaemoglobins comprise a haem domain homologous to classical globins and a ferredoxin-NADP+ reductase (FNR)-like domain that converts the globin into an NAD(P)H-oxidizing protein with diverse reductase activities. In Escherichia coli, the prototype flavohaemoglobin (Hmp) is clearly involved in responses to nitric oxide (NO) and nitrosative stress: (i) the structural gene hmp is upregulated by NO and nitrosating agents; (ii) purified Hmp binds NO avidly, but also converts it to nitrate (aerobically) or nitrous oxide (anaerobically); (iii) hmp mutants are hypersensitive to NO and nitrosative stresses. Here, we review recent advances in E. coli and the growing number of microbes in which globins are known, draw particular attention to the essential chemistry of NO and related reactive species and their interactions with globins, and suggest that microbial globins have additional functions unrelated to ,NO' stresses. [source] Genomic and Proteomic Evidence for a Second Family of Dense Core Granule Cargo Proteins in Tetrahymena thermophilaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2005GRANT R. BOWMAN Abstract. In addition to a family of structurally related proteins encoded by the Granule lattice (GRL) genes, the dense core granules in Tetrahymena thermophila contain a second, more heterogeneous family of proteins that can be defined by the presence of a domain homologous to ,/,-crystallins. The founding members of the family, Induced during Granule Regeneration 1 (IGR1) and Granule Tip 1 (GRT1), were identified in previous screens for granule components. Analysis of the recently sequenced T. thermophila macronuclear genome has now uncovered 11 additional related genes. All family members have a single ,/,-crystallin domain, but the overall predicted organization of family members is highly variable, and includes three other motifs that are conserved between subsets of family members. To demonstrate that these proteins are present within granules, polypeptides from a subcellular fraction enriched in granules were analyzed by mass spectrometry. This positively identified four of the predicted novel ,/,-crystallin domain proteins. Both the functional evidence for IGR1 and GRT1 and the variability in the overall structure of this new protein family suggest that its members play roles that are distinct from those of the GRL family. [source] What is the role of the hevein-like domain of fruit class I chitinases in their allergenic capacity?CLINICAL & EXPERIMENTAL ALLERGY, Issue 3 2002A. Dìaz-Perales Background Class I chitinases are the major panallergens in fruits associated with the latex,fruit syndrome. These enzymes contain an N-terminal hevein-like domain homologous to latex hevein, and a larger catalytic domain. The role of these domains in their allergenic capacity is still controversial. Objective We sought to evaluate the role of both domains of class I chitinases in their IgE-binding properties, using Cas s 5, the major allergen from chestnut, as a model. Methods Recombinant Cas s 5 and its deleted form, lacking the hevein-like domain, designated rCat, were expressed in Pichia pastoris using the pPIC 9 vector. Both recombinant products were purified from the supernatants of transformed yeast cultures by gel-filtration and cation-exchange chromatography. The isolated proteins were characterized by N-terminal sequencing, enzymatic activity and N-glycosylation tests, anti-chitinase and specific IgE immunodetection. Immunoblot, RAST and CAP inhibition assays were also performed. Results Both purified rCas s 5 and rCat showed the expected N-terminal amino acid sequences and an enzymatic activity similar to that of their natural counterparts isolated from chestnut seeds, and were strongly recognized by anti-chitinase antibodies. In contrast, only rCas s 5, but not rCat, bound specific IgE from sera of patients suffering from the latex,fruit syndrome, and fully inhibited IgE-binding to natural Cas s 5 in immunoblot inhibition assays. Latex hevein also exerted a strong immunoblot inhibition of IgE-binding to chestnut Cas s 5. RAST and CAP inhibition using whole chestnut extract on the solid phase, rendered inhibition levels around 70,90% for rCas s 5 and 60% for rCat, in contrast to the immunoblotting results. Conclusions Recombinant Cas s 5 behaves like natural Cas s 5 in IgE-binding assays in vitro. The hevein-like domain of allergenic class I chitinases seems to include all their main IgE-binding epitopes when tested by immunodetection and immunoblot inhibition experiments. RAST and CAP inhibition assays, on the contrary, suggest that relevant epitopes are also harboured in the catalytic domain of these allergens. [source] Activating and inhibitory nature of the murine paired immunoglobulin-like receptor familyIMMUNOLOGICAL REVIEWS, Issue 1 2001Toshiyuki Takai Summary: Clones for murine paired immunoglobulin-like receptors (PIR) were first isolated as those coding for type I transmembrane glycoproteins with six immunoglobulin-like domains homologous to human Fc,R, bovine Fc,2R, and other related receptors. However, they turned out to bind neither IgA nor other immunoglobulins in the case of the ectopic expression on COS-1 fibroblastic cells. PIR-A and B are expressed on a wide variety of cells in the murine immune system, such as in B cells, mast cells, macrophages, and dendritic cells, mostly in a pairwise fashion. PIR-A requires homodimeric Fc receptor common , chain, which harbors an immunoreceptor tyrosine-based activation motif, for its efficient cell surface expression and for the delivery of activation signaling. In contrast, PIR-B contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in its cytoplasmic portion and inhibits receptor-mediated activation signaling in vitro upon engagement with other activating-type receptors such as the antigen receptor on B cells and the high affinity Fc receptor for IgE on mast cells. ITIMs of PIR-B on macrophages and B cells have been shown to be constitutively phosphorylated in their tyrosine residues. Although the ligand for PIR still remains unknown, the transgenics and the gene-targeted mice will provide us with valuable information on their physiological roles in the immune regulation. We thank Hiromi Kubagawa for discussion. This work is supported by CREST Program of JST, Virtual Research Institute of Aging funded by Boehringer Ingelheim, and by research grants from the Ministry of Education, Science, Sports and Culture of Japan to T. Takai. [source] Folate synthesis in plants: the last step of the p -aminobenzoate branch is catalyzed by a plastidial aminodeoxychorismate lyaseTHE PLANT JOURNAL, Issue 4 2004Gilles J.C. Basset Summary In plants, the last step in the synthesis of p -aminobenzoate (PABA) moiety of folate remains to be elucidated. In Escherichia coli, this step is catalyzed by the PabC protein, a , -lyase that converts 4-amino-4-deoxychorismate (ADC) , the reaction product of the PabA and PabB enzymes , to PABA and pyruvate. So far, the only known plant enzyme involved in PABA synthesis is ADC synthase, which has fused domains homologous to E. coli PabA and PabB and is located in plastids. ADC synthase has no lyase activity, implying that plants have a separate ADC lyase. No such lyase is known in any eukaryote. Genomic and phylogenetic approaches identified Arabidopsis and tomato cDNAs encoding PabC homologs with putative chloroplast-targeting peptides. These cDNAs were shown to encode functional enzymes by complementation of an E. coli pabC mutant, and by demonstrating that the partially purified recombinant proteins convert ADC to PABA. Plant ADC lyase is active as dimer and is not feedback inhibited by physiologic concentrations of PABA, its glucose ester, or folates. The full-length Arabidopsis ADC lyase polypeptide was translocated into isolated pea chloroplasts and, when fused to green fluorescent protein, directed the passenger protein to Arabidopsis chloroplasts in transient expression experiments. These data indicate that ADC lyase, like ADC synthase, is present in plastids. As shown previously for the ADC synthase transcript, the level of ADC lyase mRNA in the pericarp of tomato fruit falls sharply as ripening advances, suggesting that the expression of these two enzymes is coregulated. [source] | |||||||||||||