Saturday, September 26, 2009

What's new for 'Trypanosomatids' in PubMed

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Search kinetoplastids OR kinetoplastid OR Kinetoplastida OR "trypanosoma brucei" OR leishmania OR brucei OR leishmaniasis OR "African trypanosomiasis"
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PubMed Results
Items 1 -5 of 5

1: Mol Biotechnol. 2009 Sep 25. [Epub ahead of print]

Recombinant Protein Expression in Leishmania tarentolae.

Basile G, Peticca M.

Hamilton Robotics Italia s.r.l., via Tadino 52, Milan, Italy, gbasile@hamilton.ch.

A variety of recombinant protein expression systems have been developed for heterologous genes in both prokaryotic and eukaryotic systems such as bacteria, yeast, mammals, insects, transgenic animals, and plants. Recently Leishmania tarentolae, a trypanosomatid protozoan parasite of the white-spotted wall gecko (Tarentola annularis), has been suggested as candidate for heterologous genes expression. Trypanosomatidae are rich in glycoproteins, which can account for more than 10% of total protein; the oligosaccharide structures are similar to those of mammals with N-linked galactose, and fucose residues. To date several heterologous proteins have been expressed in L. tarentolae including both cytoplasmic enzymes and membrane receptors. Significant advances in the development of new strains and vectors, improved techniques, and the commercial availability of those tools coupled with a better understanding of the biology of Leishmania species will lead to value and power in commercial and research labs alike.

PMID: 19779853 [PubMed - as supplied by publisher]

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2: PLoS Pathog. 2009 Sep;5(9):e1000589. Epub 2009 Sep 25.

TbPIF5 is a Trypanosoma brucei mitochondrial DNA helicase involved in processing of minicircle Okazaki fragments.

Liu B, Wang J, Yildirir G, Englund PT.

Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland, United States of America.

Trypanosoma brucei's mitochondrial genome, kinetoplast DNA (kDNA), is a giant network of catenated DNA rings. The network consists of a few thousand 1 kb minicircles and several dozen 23 kb maxicircles. Here we report that TbPIF5, one of T. brucei's six mitochondrial proteins related to Saccharomyces cerevisiae mitochondrial DNA helicase ScPIF1, is involved in minicircle lagging strand synthesis. Like its yeast homolog, TbPIF5 is a 5' to 3' DNA helicase. Together with other enzymes thought to be involved in Okazaki fragment processing, TbPIF5 localizes in vivo to the antipodal sites flanking the kDNA. Minicircles in wild type cells replicate unidirectionally as theta-structures and are unusual in that Okazaki fragments are not joined until after the progeny minicircles have segregated. We now report that overexpression of TbPIF5 causes premature removal of RNA primers and joining of Okazaki fragments on theta structures. Further elongation of the lagging strand is blocked, but the leading strand is completed and the minicircle progeny, one with a truncated H strand (ranging from 0.1 to 1 kb), are segregated. The minicircles with a truncated H strand electrophorese on an agarose gel as a smear. This replication defect is associated with kinetoplast shrinkage and eventual slowing of cell growth. We propose that TbPIF5 unwinds RNA primers after lagging strand synthesis, thus facilitating processing of Okazaki fragments.

PMID: 19779567 [PubMed - in process]

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3: J Infect Dis. 2009 Aug 1;200(3):361-9.Click here to read LinkOut

Altered proinflammatory cytokine production and enhanced resistance to Trypanosoma congolense infection in lymphotoxin beta-deficient mice.

Okwor I, Muleme H, Jia P, Uzonna JE.

Department of Immunology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.

BALB/c mice are highly susceptible to Trypanosoma congolense infection, whereas C57BL/6 mice are relatively resistant. Overproduction of interferon-gamma (IFN-gamma) and other proinflammatory cytokines contribute to death in susceptible mice. Here, we show that lymphotoxin beta-deficient (LTbeta(-/-)) mice are more resistant than wild-type (WT) mice to T. congolense infection, as shown by a lower parasitemia level and a longer survival duration. The enhanced resistance of LTbeta(-/-) mice was associated with undetectable or low serum levels of proinflammatory cytokines (i.e., tumor necrosis factor-alpha, interleukin [IL]-6, IL-12, and monocyte chemotactic protein-1). Although infected LTbeta(-/-) mice had high numbers of CD4(+)CD25(+)Foxp3(+) cells and high serum IL-10 levels, these cells were not the major producers of IL-10. Treatment of LTbeta(-/-) mice with anti-IL-10R monoclonal antibody abolished their enhanced resistance, whereas depletion of CD25(+) cells further enhanced resistance among infected WT and LTbeta(-/-) mice. These results suggest that LTbeta plays critical role in regulating the outcome of T. congolense infection in mice.

PMID: 19563258 [PubMed - indexed for MEDLINE]

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4: Genome Biol. 2009;10(4):R36. Epub 2009 Apr 15.Click here to read Click here to read References for this PMC Article, Free in PMC, LinkOut

The transferome of metabolic genes explored: analysis of the horizontal transfer of enzyme encoding genes in unicellular eukaryotes.

Whitaker JW, McConkey GA, Westhead DR.

Institute of Molecular and Cellular Biology, University of Leeds, Leeds, West Yorkshire, LS2 9JT, UK.

BACKGROUND: Metabolic networks are responsible for many essential cellular processes, and exhibit a high level of evolutionary conservation from bacteria to eukaryotes. If genes encoding metabolic enzymes are horizontally transferred and are advantageous, they are likely to become fixed. Horizontal gene transfer (HGT) has played a key role in prokaryotic evolution and its importance in eukaryotes is increasingly evident. High levels of endosymbiotic gene transfer (EGT) accompanied the establishment of plastids and mitochondria, and more recent events have allowed further acquisition of bacterial genes. Here, we present the first comprehensive multi-species analysis of E/HGT of genes encoding metabolic enzymes from bacteria to unicellular eukaryotes. RESULTS: The phylogenetic trees of 2,257 metabolic enzymes were used to make E/HGT assertions in ten groups of unicellular eukaryotes, revealing the sources and metabolic processes of the transferred genes. Analyses revealed a preference for enzymes encoded by genes gained through horizontal and endosymbiotic transfers to be connected in the metabolic network. Enrichment in particular functional classes was particularly revealing: alongside plastid related processes and carbohydrate metabolism, this highlighted a number of pathways in eukaryotic parasites that are rich in enzymes encoded by transferred genes, and potentially key to pathogenicity. The plant parasites Phytophthora were discovered to have a potential pathway for lipopolysaccharide biosynthesis of E/HGT origin not seen before in eukaryotes outside the Plantae. CONCLUSIONS: The number of enzymes encoded by genes gained through E/HGT has been established, providing insight into functional gain during the evolution of unicellular eukaryotes. In eukaryotic parasites, genes encoding enzymes that have been gained through horizontal transfer may be attractive drug targets if they are part of processes not present in the host, or are significantly diverged from equivalent host enzymes.

PMID: 19368726 [PubMed - indexed for MEDLINE]

PMCID: PMC2688927

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5: Biochem J. 2005 May 15;388(Pt 1):29-38.Click here to read Click here to read Nucleotide, References for this PMC Article, Taxonomy via GenBank, Protein, Free in PMC, Cited in PMC, LinkOut

Molecular, functional and structural properties of the prolyl oligopeptidase of Trypanosoma cruzi (POP Tc80), which is required for parasite entry into mammalian cells.

Bastos IM, Grellier P, Martins NF, Cadavid-Restrepo G, de Souza-Ault MR, Augustyns K, Teixeira AR, Schrével J, Maigret B, da Silveira JF, Santana JM.

Laboratório Multidisciplinar de Pesquisa em Doença de Chagas (CP 04536), Universidade de Brasília, 70919-970, Brasília, DF, Brazil.

We have demonstrated that the 80 kDa POP Tc80 (prolyl oligopeptidase of Trypanosoma cruzi) is involved in the process of cell invasion, since specific inhibitors block parasite entry into non-phagocytic mammalian host cells. In contrast with other POPs, POP Tc80 is capable of hydrolysing large substrates, such as fibronectin and native collagen. In this study, we present the cloning of the POPTc80 gene, whose deduced amino acid sequence shares considerable identity with other members of the POP family, mainly within its C-terminal portion that forms the catalytic domain. Southern-blot analysis indicated that POPTc80 is present as a single copy in the genome of the parasite. These results are consistent with mapping of POPTc80 to a single chromosome. The active recombinant protein (rPOP Tc80) displayed kinetic properties comparable with those of the native enzyme. Novel inhibitors were assayed with rPOP Tc80, and the most efficient ones presented values of inhibition coefficient Ki < or = 1.52 nM. Infective parasites treated with these specific POP Tc80 inhibitors attached to the surface of mammalian host cells, but were incapable of infecting them. Structural modelling of POP Tc80, based on the crystallized porcine POP, suggested that POP Tc80 is composed of an alpha/beta-hydrolase domain containing the catalytic triad Ser548-Asp631-His667 and a seven-bladed beta-propeller non-catalytic domain. Docking analysis suggests that triple-helical collagen access to the catalytic site of POP Tc80 occurs in the vicinity of the interface between the two domains.

PMID: 15581422 [PubMed - indexed for MEDLINE]

PMCID: PMC1186690

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Cited by 4 PubMed Central articles

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