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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 55 (2001), S. 709-742 
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Comparative analysis of bacterial, archaeal, and eukaryotic genomes indicates that a significant fraction of the genes in the prokaryotic genomes have been subject to horizontal transfer. In some cases, the amount and source of horizontal gene transfer can be linked to an organism's lifestyle. For example, bacterial hyperthermophiles seem to have exchanged genes with archaea to a greater extent than other bacteria, whereas transfer of certain classes of eukaryotic genes is most common in parasitic and symbiotic bacteria. Horizontal transfer events can be classified into distinct categories of acquisition of new genes, acquisition of paralogs of existing genes, and xenologous gene displacement whereby a gene is displaced by a horizontally transferred ortholog from another lineage (xenolog). Each of these types of horizontal gene transfer is common among prokaryotes, but their relative contributions differ in different lineages. The fixation and long-term persistence of horizontally transferred genes suggests that they confer a selective advantage on the recipient organism. In most cases, the nature of this advantage remains unclear, but detailed examination of several cases of acquisition of eukaryotic genes by bacteria seems to reveal the evolutionary forces involved. Examples include isoleucyl-tRNA synthetases whose acquisition from eukaryotes by several bacteria is linked to antibiotic resistance, ATP/ADP translocases acquired by intracellular parasitic bacteria, Chlamydia and Rickettsia, apparently from plants, and proteases that may be implicated in chlamydial pathogenesis.
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Mutations and/or overexpression of various transporters are known to confer drug resistance in a variety of organisms. In the malaria parasite Plasmodium falciparum, a homologue of P-glycoprotein, PfMDR1, has been implicated in responses to chloroquine (CQ), quinine (QN) and other drugs, and a putative transporter, PfCRT, was recently demonstrated to be the key molecule in CQ resistance. However, other unknown molecules are probably involved, as different parasite clones carrying the same pfcrt and pfmdr1 alleles show a wide range of quantitative responses to CQ and QN. Such molecules may contribute to increasing incidences of QN treatment failure, the molecular basis of which is not understood. To identify additional genes involved in parasite CQ and QN responses, we assayed the in vitro susceptibilities of 97 culture-adapted cloned isolates to CQ and QN and searched for single nucleotide polymorphisms (SNPs) in DNA encoding 49 putative transporters (total 113 kb) and in 39 housekeeping genes that acted as negative controls. SNPs in 11 of the putative transporter genes, including pfcrt and pfmdr1, showed significant associations with decreased sensitivity to CQ and/or QN in P. falciparum. Significant linkage disequilibria within and between these genes were also detected, suggesting interactions among the transporter genes. This study provides specific leads for better understanding of complex drug resistances in malaria parasites.
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] NF-κB transcription factors mediate the effects of pro-inflammatory cytokines such as tumour necrosis factor-α and interleukin-1β. Failure to downregulate NF-κB transcriptional activity results in chronic inflammation and cell death, as observed in A20-deficient mice. A20 ...
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 222 (2003), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Numerous bacterial transcription factors contain a DNA-binding helix-turn-helix domain and a signaling domain, linked together in a single polypeptide. Typically, this signaling domain is a small-molecule-binding domain that undergoes a conformational change upon recognizing a specific ligand. The HutC/FarR-like transcription factors of the GntR family are one of the largest groups of transcription factors in the proteomes of most free-living bacteria. Using sensitive sequence profile analysis we show that the HutC/FarR-like transcription factors contain a conserved ligand-binding domain, which possesses the same fold as chorismate lyase (Escherichia coli UbiC gene product). This relationship suggests that the C-terminal domain of the HutC/FarR-like transcription factors binds small molecules in a cleft similar to the substrate-binding site of the chorismate lyases. The sequence diversity within the predicted binding cleft of the HutC/FarR ligand-binding domains is consistent with the ability of these transcription factors to respond to diverse small molecules, such as histidine (HutC), fatty acids (FarR), sugars (TreR) and alkylphosphonate (PhnF). UbiC-like chorismate lyases function in the ubiquinone biosynthesis pathway, and have characteristic charged, catalytic residues. Genome comparisons reveal that chorismate lyase orthologs are found in several bacteria, chloroplasts of eukaryotic algae and euryarchaea. In contrast, the GntR transcription regulators lack the conserved catalytic residues of the chorismate lyases, and have so far been detected only in bacteria. An ancestral, generic small-molecule-binding domain appears to have given rise to the enzymatic and non-catalytic ligand-binding versions of the same fold under the influence of different selective pressures.
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  • 5
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Using computational analysis, a novel superfamily of β-strand-rich domains was identified in the Molybdenum cofactor sulfurase and several other proteins from both prokaryotes and eukaryotes. These MOSC domains contain an absolutely conserved cysteine and occur either as stand-alone forms such as the bacterial YiiM proteins, or fused to other domains such as a NifS-like catalytic domain in Molybdenum cofactor sulfurase. The MOSC domain is predicted to be a sulfur-carrier domain that receives sulfur abstracted by the pyridoxal phosphate-dependent NifS-like enzymes, on its conserved cysteine, and delivers it for the formation of diverse sulfur–metal clusters. The identification of this domain may clarify the mechanism of biogenesis of various metallo-enzymes including Molybdenum cofactor-containing enzymes that are compromised in human type II xanthinuria.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 176 (1999), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mutations in the cytoplasmic linker regions of receptor histidine kinase and chemoreceptor proteins have been shown previously to significantly impair receptor functions. Here we demonstrate significant sequence similarities between these regions in numerous histidine kinases, methyl-accepting proteins, adenylyl cyclases and other prokaryotic signalling proteins. It is suggested that these ‘HAMP domains’ possess roles of regulating the phosphorylation or methylation of homodimeric receptors by transmitting the conformational changes in periplasmic ligand-binding domains to cytoplasmic signalling kinase and methyl-acceptor domains.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 29 (2005), S. 0 
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The helix-turn-helix (HTH) domain is a common denominator in basal and specific transcription factors from the three super-kingdoms of life. At its core, the domain comprises of an open tri-helical bundle, which typically binds DNA with the 3rd helix. Drawing on the wealth of data that has accumulated over two decades since the discovery of the domain, we present an overview of the natural history of the HTH domain from the viewpoint of structural analysis and comparative genomics. In structural terms, the HTH domains have developed several elaborations on the basic 3-helical core, such as the tetra-helical bundle, the winged-helix and the ribbon-helix–helix type configurations. In functional terms, the HTH domains are present in the most prevalent transcription factors of all prokaryotic genomes and some eukaryotic genomes. They have been recruited to a wide range of functions beyond transcription regulation, which include DNA repair and replication, RNA metabolism and protein–protein interactions in diverse signaling contexts. Beyond their basic role in mediating macromolecular interactions, the HTH domains have also been incorporated into the catalytic domains of diverse enzymes. We discuss the general domain architectural themes that have arisen amongst the HTH domains as a result of their recruitment to these diverse functions. We present a natural classification, higher-order relationships and phyletic pattern analysis of all the major families of HTH domains. This reconstruction suggests that there were at least 6–11 different HTH domains in the last universal common ancestor of all life forms, which covered much of the structural diversity and part of the functional versatility of the extant representatives of this domain. In prokaryotes the total number of HTH domains per genome shows a strong power-equation type scaling with the gene number per genome. However, the HTH domains in two-component signaling pathways show a linear scaling with gene number, in contrast to the non-linear scaling of HTH domains in single-component systems and sigma factors. These observations point to distinct evolutionary forces in the emergence of different signaling systems with HTH transcription factors. The archaea and bacteria share a number of ancient families of specific HTH transcription factors. However, they do not share any orthologous HTH proteins in the basal transcription apparatus. This differential relationship of their basal and specific transcriptional machinery poses an apparent conundrum regarding the origins of their transcription apparatus.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 183 (2000), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sequence analysis of the recently identified class I aldolase of Escherichia coli (dhnA gene product) helped to identify its homologs in Chlamydia trachomatis, Chlamydiophyla pneumoniae and in each of the completely sequenced archaeal genomes. Iterative database searches revealed sequence similarities between the DhnA-family enzymes, deoxyribose phosphate aldolases and bacterial (class II) fructose bisphosphate aldolases and allowed prediction of similar three-dimensional structures (TIM-barrel fold) in all these enzymes. The Schiff base-forming lysyl residues of DhnA and deoxyribose phosphate aldolase are conserved in all members of the DhnA and deoxyribose phosphate aldolase families, indicating that these enzymes share common features with both class I and class II aldolases. The DhnA-family enzymes are predicted to possess an aldolase activity and to play a critical role in sugar biosynthesis in archaea.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 197 (2001), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A previously undetected conserved domain is identified in two distinct classes of tRNA-modifying enzymes, namely uridine methylases of the TRM2 family and enzymes of the MiaB family that are involved in 2-methylthioadenine formation. This domain, for which the acronym TRAM is proposed after TRM2 and MiaB, is predicted to bind tRNA and deliver the RNA-modifying enzymatic domains to their targets. In addition to the two families of RNA-modifying enzymes, the TRAM domain is present in several other proteins associated with the translation machinery and in a family of small, uncharacterized archaeal proteins that are predicted to have a role in the regulation of tRNA modification or translation. Secondary structure prediction indicates that the TRAM domain adopts a simple β-barrel fold. In addition, sequence analysis of the MiaB family enzymes showed that they share the predicted catalytic site with biotin and lipoate synthases and probably employ the same mechanism for sulfur insertion into their respective substrate.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 48 (1999), S. 291-302 
    ISSN: 1432-1432
    Keywords: Key words: RNA-binding domains — Ribosomal protein S4 — Archaeosine transglycosylase — Pseudouridine synthase — Translation machinery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Two previously undetected domains were identified in a variety of RNA-binding proteins, particularly RNA-modifying enzymes, using methods for sequence profile analysis. A small domain consisting of 60–65 amino acid residues was detected in the ribosomal protein S4, two families of pseudouridine synthases, a novel family of predicted RNA methylases, a yeast protein containing a pseudouridine synthetase and a deaminase domain, bacterial tyrosyl-tRNA synthetases, and a number of uncharacterized, small proteins that may be involved in translation regulation. Another novel domain, designated PUA domain, after PseudoUridine synthase and Archaeosine transglycosylase, was detected in archaeal and eukaryotic pseudouridine synthases, archaeal archaeosine synthases, a family of predicted ATPases that may be involved in RNA modification, a family of predicted archaeal and bacterial rRNA methylases. Additionally, the PUA domain was detected in a family of eukaryotic proteins that also contain a domain homologous to the translation initiation factor eIF1/SUI1; these proteins may comprise a novel type of translation factors. Unexpectedly, the PUA domain was detected also in bacterial and yeast glutamate kinases; this is compatible with the demonstrated role of these enzymes in the regulation of the expression of other genes. We propose that the S4 domain and the PUA domain bind RNA molecules with complex folded structures, adding to the growing collection of nucleic acid-binding domains associated with DNA and RNA modification enzymes. The evolution of the translation machinery components containing the S4, PUA, and SUI1 domains must have included several events of lateral gene transfer and gene loss as well as lineage-specific domain fusions.
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